Are London Heathrow's ULTra Pods the Future of Transit?

Proponents of personal rapid transit systems have frequently promoted themselves as opponents of traditional public transportation. Unlike expensive metro or light rail systems, they claimed, their PRT lines would be cheaper to construct, more convenient for passengers, and more attractive for users. Now that a new line is readying for opening in the United Kingdom, the technology may attain new prominence.

Over the years, most attempts at implementing PRT have failed due to a lack of interest from investors — and as a result of deceptive, dishonest campaigns by “pod people” who simply promise too much.

Even with the rebirth of modern rail systems over the past few decades in the United States, PRT continues to be brought up as an environmentally friendly solution for urban transport, allowing passengers virtually instant access to vehicles, stop-free commutes, and direct access to many destinations. In other words, it theoretically can solve many of the deficiencies of regular transit, which requires waiting for trains or buses to arrive, multiple stops along a route, and a walk or drive to and from stations. Yet only in 1975, at the University of West Virginia in Morgantown, has a system that allows such on-demand travel by automated train been constructed.

Next spring, London’s Heathrow Airport will take a step forward to advance the PRT concept with the implementation of a new network connecting its Terminal 5 and associated parking areas. The ULTra (Urban Light Transit) system is being developed by Bristol, England Wales-based Advanced Transport Systems and will initially travel between three stations along a three-mile track using 21 four-passenger vehicles. The mini-cars, which travel at speeds of up to 25 mph and which use lasers for guidance along the 7 foot-wide pavement, have tires and are autonomous, meaning they more closely replicate the experience of automobiles than trains. They’re battery driven and use energy at the equivalent of 200 mpg.

Vehicles are designed to bypass stations, allowing non-stop travel. Customers will pick their destination by pressing a button on a touch screen before departing. Empty vehicles will be available at all times at stops for passengers needing to get between the car parks and the airport terminals, or vice-verse.

The system didn’t come cheaply — at $41 million, the private airport owner that paid for the line and some of the technology’s development is making a big bet that it hopes to eventually expand throughout the airport and into the surrounding areas with 400 pods at a cost of $330 million. That is, if this first test goes well.

If the claimed $7-15 million costs per mile (without rights-of-way) are to be believed, this PRT is cheaper than normal transit, but not much. Per passenger, its costs may actually be higher, since it is only expected to handle about 500,000 annual passengers, an average of less than 2,000 a day.

Nevertheless, the system holds promise: its use of batteries installed in each vehicle rather than an electrified third rail or catenary makes the corridor easier to maintain and cheaper to build — an advantage that will soon be replicated in the implementation of similar technology on tramways. The use of electricity rather than diesel motors (as in the existing buses used by passengers) will eliminate local-source pollutants and decrease noise levels. The elimination of human drivers will improve travel times by 60% and reduce operating costs by 40% — if initial estimates prove accurate. Passengers will get direct and instant access between parking lots and the terminal; plus, they’ll eventually be offered similar service to surrounding office buildings and hotels.

Unlike the cities in which PRT lines are usually proposed, this airport environment provides a sealed-off, protected setting in which to experiment with this model for a new form of transportation. The ULTra project seems highly likely to operate problem-free here, but what is the appeal elsewhere?

Abu Dhabi is planning a new city called Masdar that will not allow cars and instead rely on PRT lines to connect people from one place to another; San Jose is planning a people mover between its airport and surrounding transit stations and neighborhoods; other American cities like Mountain View and Ithaca are “studying” the idea, though there are no definite plans there. Companies such as SkyCab and Vectus are planning their own rival PRT technologies to spread around the world, and unlike some previous PRT pushers, they seem truthful in what they expect to provide (in other words, they don’t claim that initial capital costs will be paid back with fare revenue).

For airports and new cities, PRT could supplement other mass transit systems rather effectively and encourage people to live car-free lifestyles by providing them destination-to-destination service with minimal walking to and from stations. In newly built environments, PRT could be constructed cheaply and it could be installed in such a way that does not disrupt its surroundings. Proponents use this fact as evidence for the universal applicability of PRT, claiming that it should replace transit systems since it would allow for the phase out of cars, but their arguments are weakened by the realities of the way cities work.

PRT cannot replace light and metro rail systems, as its capacity is far lower. Along major routes at peak periods, systems that are capable of carrying hundreds of people per train every two minutes are necessary, and PRT will never allow that kind of operation.

Similarly, if a PRT vehicle sounds awfully like an automated car, the analogy isn’t far off: indeed, the idea that people would be able to travel by themselves from one place to another is simply an advanced version of the car sharing systems now being implemented in places like Paris. Most major cities have serious transportation needs along heavily traveled lines, and PRT will not be able to do much there, since the lines would be completely overloaded and therefore unusable if implemented in very dense cities like New York or San Francisco.

In addition, PRT’s proponents ignore the fact that their calls for dense networks of lines and stations would duplicate the already existing road system and degrade the urban landscape with elevated structures. This is no effective already to urban sprawl, since direct access to PRT stations every few blocks would undoubtedly encourage the sort of spread-out environments that have blighted American cities for decades. For those that don’t care about that problem, a cheaper alternative might be to wait a decade or so for more advanced automobiles that can negotiate existing streets without drivers. Stations wouldn’t be needed for such a system — people could simply call an automated service, and a robotized car would arrive in front of the house. This is no less a fantasy than the installation of hundreds of miles of PRT tracks above city streets.

This experiment at Heathrow Airport, then, will test some of the basic arguments of PRT advocates and probably verify many of their claims about the system’s effectiveness, but it won’t provide a solution to the deeper problems with the idea.

Note to readers: Discussions of PRT frequently produce angry debate. There’s nothing wrong with spirited interchange, but let’s try to restrain ourselves from personal insults. They are not acceptable here and will be deleted. Image above: ULTra in action at Heathrow, from Advanced Transport Systems Ltd

I think of bikesharing (with protected bike lanes connecting the bikesharing stations) as the low-tech version of PRT. Bikesharing wouldn’t work in this particular Heathrow application because of travelers luggage. But in many cases, it’s worth comparing the two.

Here in Chicago we have this long-established PRT system that provides pretty much 100% coverage to the greater downtown area and most of the north lakefront. It allows me to walk out of any building, send a signal, and go directly to any other location in a 4-person pod, without ever having to stop for others to get into or out of the pod. It’s not automated, however, and uses the ordinary city streets. We call it “taxi”.

I think PRT is an excellent way of solving the “last mile” problem faced by transit planners. It is ridiculous to think PRT could replace higher capacity urban transit (light rail, subway and certain bus lines) in certain areas like the inner city. But to take people from a transit stop to close to their home, or for inner suburban type travel, such as home to town center, schools (think about how much waste comes from diesel school buses in many suburbs and cities), shopping centers, etc, PRT could make sense. Roads themselves can only handle so many cars, and taxis are less than convenient outside of most inner city areas since you need to call for them and wait. People aren’t willing to do that.

My main problem with PRT is the track. The idea of elevated tracks everywhere is not appealing, but I’m not sure other options would work, or be accepted.

That is something I have wondered ever since I started hearing of ‘PRT’. On a fixed guideway – of any type – one cannot pass unless there is a dedicated structure there, such as a passing siding on railroads.

I can just see the jam behind one of these things when you have a out of town family trying to load (or unload) packages and luggage and it takes more than a few seconds to get going.

Also where do the ‘excess’ pods stack up while awaiting a call? Taxis have taxi stands and such but will each block have a miniature rail yard storing these things?

PRT “stops” (they’re really too small to be called “stations”) are offline. Through traffic proceeds on the mainline, while your out-of-towners are wrestling with the luggage and the kids. Merging into and out of mainline traffic is handled automatically, at the maximum safe possible speed to do so. On the mainline, traffic also proceeds at the maximum safe possible speed, so there isn’t any “passing.” Excess pods can be handled a number of ways. The most obvious is to automatically distribute “empties” around the system so that vehicles are always waiting for passengers, and not the other way around. But at times of light-traffic, an excess of empty vehicles (or any that were rejected by potential passengers because of being dirty or damaged) would collect at a maintenance barn.

Actually, I like simple’s solution. The problem with taxis, however, is that they’re a little pricey, and can be hard to find outside of certain business and entertainment districts. The problem is created by the fact that most municipalities restrict the number of taxis. If these restrictions were lifted, taxis might be cheaper and easier to find, helping to solve the “last mile” problem that Geoff refers to.

The PRT track system is set up so the pods move off the main line track to a loop track into the station, so passing pods can continue on the main line track to their destinations being interrupted by stopping pods. At busy stations, I would assume the station track would be of a significant enough length to hold some pods there for easy access. I think most systems are planned with the idea that pods will constantly move (or maybe be placed on offshoot tracks for waiting around the system), so they will be called up and arrive within a minute or two to the station to pick a person up.

As I said, busy stations and busy routes would need to continue to use more traditional transit that is better suited for moving large numbers of people to highly used areas.

There is a wide range of capacity in rail systems. At the high end, there are the metro rail systems which carry 500-1000 passengers every two minutes, for a total maximum capacity of 15,000-30,000 passengers per hour. Most PRT proponents do NOT aim to compete with nor replace these systems.

In contrast, many streetcars run every 6 minutes and carry a few hundred passengers, giving a maximum capacity of less than 5000 passengers per hour. It is these systems against which PRT more directly competes. There are hundreds of these lower-density city-based applications across the world, where PRT would be a good option.

As for “replicating the road system”, roads are being expanded all the time because they can’t handle capacity. Rather than turning a 2 lane street with street parking into a 5-lane arterial, as is often done in response to congestion, PRT proposes to add a narrow-guage elevated guideway (smaller than a pedestrian crosswalk) which will carry as much or more than the lane expansion. When compared to increased lanes of bumper-to-bumper automobile traffic, the prospect of a lightweight elevated structure doesn’t seem so “degrading” if it can keep the streets walkable.

So while you may think of PRT as a “degrading replication”, I think of it as “less disruptive *augmentation*” of the road system.

Automated cars which can operate on streets are a LONG way off. From a technical standpoint, operating vehicles in a mixed-mode environment is *orders-of-magnitude* more complex than operating on an exclusive guideway. And even if automated cars were here today (far from it), they do not solve the congestion problem on our already-overburdened streets.

The bottom line is this: many city streets are clogged with non-pedestrian traffic, and it’s getting worse every year. For big cities, metro rail systems are highly effective at relocating much of this traffic underground, but there are hundreds of cities which are too small to justify a metro — in those cities, PRT would be the cheapest and most effective way of moving traffic off the street.

If you think of PRT as a substitute for *roads* rather than a substitute for *rail*, then sure, it does kind of make sense.

Except then it’s too expensive!

It has to be fully grade-separated, and the reason roads get built is that they *don’t* have to be fully grade separated.

What would PRT be a good substitute for, then? Grade-separated roads? I guess so. It would be a decent replacement for expressways…. except that the PRT pods can’t go onto the local roads from the expressways, so they lose that advantage, meaning that high-capacity rail makes more sense….

Now, design me a set of passenger cars which are ‘roadrailers’ and can merge onto an automated “PRT superhighway”, and you have a *serious* idea.

I was hiking along the rivers edge in Cardiff earlier this summer when I came across the test track for the ULTRA PRTs pictured. I was quite weird to come across it in such a setting! I watched them for a bit circle around the track and into and out of the stations. Yes – there is a separate siding for the stations, allowing other pods to get by if not stopping there. The cars were quite quiet – just the hum of the wheels on concrete as they passed. The cars I saw got up to maybe 20 mph (I would guess), slowing as they pulled into the station.

For an airport like Heathrow, it would probably work well, as the terminals are scattered across the property in a non-linear way (unlike – for example – Denver International).

The small people mover in West Virginia looked like a real good one in that it went from several major places on a Campus and it is still around after the 1970’s expiramental project which is good. I think they could try another exparament with that same WA system by extending it two or three miles to a major shopping center or mall and see how it handles outside of a one campus system. But I think these systems might do well in large Office complexes or Shopping centers possibly amusement parks were you need a good local people mover system. If they had to buid a underground tunnel for this system they could use giant cement box culvert sections and put that under the streets for them to run in. I would like to see the West Virginia system exended a little.

Something like the Aerobus technology would make for cheaper elevated track, with the pod suspended from light rail track laid on suspension cable. On a PRT system rather than a LRT like system, the stop could well be at ground level with the stop siding dropping down and then under the through track.

A six person capacity at 35mph with only requested stops would make for a fine local-transport and last-five-miles system, feeding into a higher capacity rail backbone.

It may be that part of the over-promising of PRT advocates comes from trying to sell it as a one-size-fits-all transport solution, even though we are still laboring under the burdens imposed by the last big assumption that a one-size-fits-all system actually exists – as the car-based system proved, yet again, that one-size-fits-all fits many poorly and never actually does fit ALL.

The last mile problem was already solved by the bus. Going 20 miles on a bus sucks. Traveling a mile or two on the bus is a breeze. Unfortunately, many people think they are too good for the bus.

Over in Anaheim PRT is or was one of the alternatives for the ARTIC to Garden Walk Ghost Mall Fixed Guideway project. I think monorail is the front runner for this project, but the point is the same. People want to implement outrageous technologies such as PRT or monorail when a rapid bus can do the exact same thing for less money, and serve a hell of a lot more people. ARTIC will feature underground bus terminals for easy transfers from high speed and regular rail. The bus stop at Katella and Harbor will get you just as close to the Disneyland area as the ARTIC stops.

I think many of the advantages of these pods could (and perhaps should) be incorporated into conventional transit. It’s hard to imagine automating a bus on the street, but not hard to image automating a subway – which already operates on an exclusive guideway. Do that and it suddenly becomes much cheaper to operate express serve and local service. Instead of running trains every 6, 8 ,15 minutes, shorter trains are run requiring less cars in total because the express trains will finish their routes faster. It’s just like the pods, only 100 person pods!

Christopher Parker, several new Metros (subway/elevated heavy rail systems) have in fact been automated. The Dubai metro has no driver, and a couple Paris lines are also automated, with platform doors to prevent passengers from getting caught. BART was originally designed the be automated, and probably could be with upgrades to the platforms (the problem is people getting caught in doors if there is no driver to look out for them).

However, many of these systems are planned for peak headways under 3 minutes. When you are running full-length trains that often in rush hour, there is no room for anything extra as you suggest. The real advantage comes in off-peak times, when you can run shorter trains more frequently a lower cost, with no driver’s wages to pay.

Unfortunately, express trains require more than two tracks (for safety) at least near the local stations, if operated frequently. If the subway was not built that way, express trains are only possible at a low frequency, maybe every 15 minutes, depending on the length of the route.

I agree that many of the benefits of PRT can be had by bike-sharing or car-sharing programs at a fraction of the cost. Most adults know how to drive a car and ride a bike, so why build an automated, grade-separated system? For the last-mile problem, biking or driving slowly at 10 mph is plenty fast (a mile is a 20 minute walk, but only 5 minute bike ride). For long-distance travel, over 5 miles or so, PRT will never have enough capacity.

At airports, where walking or biking are often not possible, buses and automated light rail work well (guess which is cheaper…) as long as all the main destinations are more or less along one line or loop. Heathrow’s crazy airport design, with terminals, hotels, car rentals and the Tube station scattered all around, may be one of the few places that PRT could make sense.

Taxis can be a great means of getting around in cities with few private cars and low wages. In Lima, Peru ten years ago the city streets were almost entirely devoted to cheap taxis ($1 a ride for a few miles) and cheaper buses ($0.10?), with high average speeds on the main boulevards. I hear that traffic is much worse now that the middle class have all bought cars. The same thing happened in the 00’s in San Jose, Costa Rica and in other cities. In Europe and North America, where high costs limit taxis to rare occasions or use by the rich, car-sharing is a much better alternative.

I think that one reason there is so much hostility to PRT among transit advocates, is the same reason BRT raises hackles: Many see it as a Trojan horse advocated by anti-transit forces to try and prevent effective transit from being deployed. Some PRT supporters seem to plug it as a silver bullet, not a technology which might solve some problems but isn’t the answer to anything.

Is that fair? Probably not. But PRT (assuming that community-scale PRT systems can be efficiently built) is fighting with the tried-and-true for scarce dollars (or Euros or whatever) in many places, and seems to be positioned as an alternative to busses or trains.

Which is unfortunate–as PRT, if feasible, would be instead an alternative to cars and roads.

The “killer app” for PRT is a community of lower density where the dichotomy of walking (or cycling) vs mass transit isn’t entirely feasible–where the density is low enough that quality transit service (comprehensive and with short headways) is too prohibitive, and distances are too far to walk conveniently. Right now this niche is served by the personal automobile, with the result that a) acres of real estate is taken up by roads and parking spaces, and b) lots of short trips involve hauling around one-ton hunks of metal burning hydrocarbons, often to transport a couple hundred kilos of human flesh, or less.

But what if–and here I’m engaging in some sci-fi speculation here, as the technology is not ready for real-world deployment–subdivisions didn’t come with garages, driveways, and wide streets down the middle, but instead with small PRT networks providing access to local services, and/or to mass transit for longer trips? Some streets (for traditional vehicles) might be provided, for things like deliveries or service access, but private autos would be greatly restricted. (If you wanted to own one, it would be stored elsewhere, and reachable via PRT or mass transit). Now retrofitting an existing neighborhood with such a thing would probably be a difficult sell, but if (again assuming mature technology) constructing a new one around a PRT network, as opposed to a street network, were cost-effective, it might be a viable urban form.

Many urban advocates might ask “why bother”? The obvious answer is that not everyone WANTS to live in high-density areas, especially ones that involve apartments or other communal living arrangements. The single-family detached home is highly valued by many, and right now, such living arrangements aren’t served as well by transit–which makes residents thereof want (nay, need) to own autos, which requires all the auto infrastructure, which results in sprawl. And once you have the auto or two, and drive to work and back, who cares about the bus?

Many suburban dwellers, of course, fear that they will be left behind in a post-auto society–either abandoned, as the cities once were by suburbia, or herded at gunpoint into bloc housing (such ridiculous and fantastic elements do seem to have a prominent place in right-wing anti-transit propaganda). But the main issues with many suburbs are that a) separation of housing and commerce makes even the shortest trip impractical without a vehicle of some sort, and b) the low density makes mass transit a dubious proposition. Re-zoning can help with A in some cases, but b) remains an issue.

If PRT is to contribute to the cities of tommorow–a big if, assuming the technology can be matured and deployed at low cost (or at least comparable cost to paving everywhere)–this is the niche I think it will play. PRT deployments should be neighborhood scale, not urban scale. Or university or airport scale, given the few production deployments mentioned in the lead. Discussion of an urban PRT system is wrongheaded, misleading, and foolish–instead we should discuss numerous separate PRT systems, deployed on a piecemeal basis, interconnected by traditional mass transit.

PRT requires a fair amount of infrastructure — possibly less than light rail, but not by much. But what does a low-capacity PRT serve?

If it’s to be used as a last-mile-whatever, then that means it needs to be a comprehensive network — which is an absurdly large amount of infrastructure to serve something that cannot be high-density, simply because PRT cannot carry a high capacity. So you can’t build it everywhere. But where do you choose to build it? In the… high-capacity corridors of the low-density area that doesn’t warrant light rail infrastructure?

Really, what problem is PRT trying to solve? Transit infrastructure must be related to land use, and vice versa. What kind of land use warrants PRT, and what kind of land use does PRT support? And how much PRT infrastructure do you need to have a comprehensive system? Until these kinds of questions are addressed, PRT is just not a serious proposal for urban transit.

Standard suburbs require a fair amount of infrastructure–streets, traffic signals, parking, enforcement, souped-up drainage systems to deal with the fact that pavement does not absorb water. Often times this cost is borne by developers and their customers (homebuyers), other times it gets paid for out of general funds.

For PRT to be successful, it would need to REPLACE all of this, not be in ADDITION to it.

Light rail is cheaper than freeways with equivalent people-moving capacity, after all…

The solution to the problems of mass transit in suburbia isn’t PRT, it’s infill.

“how can we make mass transit work in suburbia” is a nonsensical question. It’s like asking how you can make 2+2 equal 5.

Cars are PRT. If the human-guided pods aren’t working anymore, you’re not living in suburbia anymore and you need to embrace your new urban overlords, that means infill and true mass transit. Choke down your brown fear and buy a bus pass.

The problem with buses is that they have to run on a schedule, and therefore are either overcrowded or underused. A bus system couldn’t compete with a PRT system for efficiency. Buses are cheap though, but cheap doesn’t always mean better.

Another area where I think PRT is important and beats out the car is for the less urban areas with children and seniors. Neither can, or in some cases, shouldn’t drive a private car, but need to get to places, school, doctors, grocery, etc, which are often grouped anyway. A well planned system, assuming a less sprawling town, would be excellent in this situation.

There are a wide range of PRT systems in development today. The current generation ULTra PRT system has a maximum capacity of about 1200 passengers per hour on any given “line” (based on 3 second headways), which is about equivalent to a 72-passenger bus running at 3.5 minute frequency, or a 150-passenger streetcar at 7 minute frequency.

In other words, current generation PRT has the capacity to handle the same kinds of loads of existing light transit modes.

But that is not the end of the story for PRT capacity. ULTra’s design permits headways down to 1 second, which would triple capacity to more than 3000 passengers/hr, the equivalent of a 200+ passenger train running every 4 minutes. One second headways are safe at 25mph (it’s about 1.5 car lengths following distance in an automobile), but transit regulators have never had to deal with a system like PRT, so the regulations are evolving. ULTra is (wisely) starting out with a light capacity version to gain real world operational experience, which will provide invaluable feedback for the eventual transition to shorter headways.

And there’s more. Some PRT vendors have taken a hybrid approach, with larger, “group” vehicles augmenting the personal vehicles. In the late 1970s, Cabinentaxi (Germany) fully developed a system that ran at 2.5 seconds separation and had 3 vehicle sizes: 3/12/18 passengers. This system was fully tested and safety-approved, and with the 18-passenger vehicle could carry tens of thousands of passengers per hour, while still retaining the fully personal capability for off-peak travel.

So when we hear “PRT is low capacity”, we need to realize that it’s a much more complicated story than that. Current versions are light, but still equivalent to a high frequency city bus or small streetcar; next generation versions will be on par with many light rail systems, and the future could bring PRT systems with the capacity of a low end metro. But it has to start somewhere, so light capacity systems are the current norm.

I think Mike C. makes an important point. PRT offers the prospect of a rail network with much more flexible operation. On one extreme it could run all scheduled transit, or on the other an optimized unscheduled service that uses past demand and real time requests to deploy vehicles as efficiently as possible. Or you could provide a hybrid approach. In any case, I’d rather the bus waited for me, than I waited for the bus.

Bigger vehicles do offset an important advantage of PRT – the relatively lean structural requirements. My guess is that you wouldn’t want to go beyond a capacity of ten to lose this advantage.

I also think that PRT offers a much stronger prospect of PPP than traditional transit. In the Mountain View/Santa Clara/San Jose instance, the Intels, Ciscos, Apples, Googles, Oracles, Genentechs, Adobes, major hospitals, SCUs, Stanfords, De Anza Colleges, etc that might want to expand on their limited real estate could see a PRT extension as a nice option to placate the neighborhood and address community concerns about traffic, etc. while pursuing infill and density. Infill is nice, if you can get your residents to agree to it. Unfortunately, wealthier communities (most of San Mateo and Santa Clara counties) don’t really want density in their backyard and more traffic on their streets.

Mike C, the capacity of light rail is much higher than 1,200 passengers per direction per hour; Vukan Vuchic’s book gives it as 20,000, and systems with few grade crossings, such as Calgary, are capable of 30,000. Even a highway lane could do better than 1,200 – when there are multiple lanes, the capacity of each lane is 1,800-2,000 cars per hour.

Vuchic also gives the capacity of a city bus with 4 lanes and a dedicated ROW as 15,000; with articulated buses, 2 lanes are enough.

@Alon: I think Mike C’s estimate is reasonable for streetcars. The better comparison is with an arterial lane which would run more in the neighborhood of 900 vehicles per hour.

One further point: APMs have developed a niche market around the country at airports, hospitals, and Las Vegas Resort hotels. Private developers seem to view these systems as cost effective. I would think that PRT would be the next extension of this idea – an open source version. The Strip might not be every planner’s dream, but it functions surprisingly well as a pedestrian environment. I think that the old rectilinear conception of a city isn’t necessarily the only way to do things. Central Las Vegas manages to use space in innovative ways and it provides interesting lessons for the PRT crowd.

Alon, I didn’t claim light rail is 1200, I said a bus or streetcar, which is a low-end rail system.

The fact is, “light rail” is a moniker that is applied to a wide range of systems, from streetcars carrying less than 3000 passengers per hour, to fully grade-separated long-platform systems with capacities in the tens of thousands. But it’s important to realize that once you enter the realm of grade-separated rail, costs go up *significantly*, likely over $100M per mile. The recently completed Seattle light rail has (I believe) over 10,000 passengers per hour max capacity, but that was over $150M per mile to build.

When rail systems are at the street level, mixing with automobile/bus/pedestrian cross traffic, capacities are generally limited to no more than 5000-7000 max, because the traffic constraints restrict the frequency and train size. As an example, a 3-car train carrying 600 passengers and running at 6 minute frequency is 6000 passengers per hour. In most city applications, it would be difficult to run street level rail with larger trains than this, or at higher frequency, due to the limitations of operating on the street.

So capacities in the tens of thousands are possible with rail, but it requires at least semi-exclusive right-of-way, which is both expensive and disruptive. Same with high capacity bus systems. This is not to say that these systems don’t have merit, just that when comparing capacity to PRT, it should be an apples to apples comparison, and comparing a $150M/mile grade-separated rail line to PRT on a pure capacity basis is not apples-to-apples.

When both costs AND capacity are taken into account, PRT is quite competitive while providing a higher level of service.

Seattle has had the highest per-mile cost of any North American light rail system, because it was built with metro infrastructure. Most light rail systems are physically separated but not grade separated, running in freight rail or freeway rights of way, and cost much less; the North American average excluding Seattle is $35 million per mile. Physical separation ensures high capacity and reliability, and the busier systems, such as Calgary’s, are already planning for a capacity of 20,000 passengers per direction per hour or higher.

I’m not sure where you get the idea that it’s difficult to run trains more frequently than once every 6 minutes. Light rail can reliably run at-grade once every 2 minutes. In North America it hasn’t happened yet because of low ridership, but Calgary comes close: its two lines run every 5 minutes at rush hour, for a frequency of once train every 2.5 minutes on the shared trunk line in the downtown transit mall.

Before 1940 it worked all over the world. In the US they are now known as trolley suburbs. Very nice if you don’t mind putting your single family house on a 35 by 75 lot. Still works in the rest of the world.

But it has to start somewhere, so light capacity systems are the current norm.

Vaporware is the current norm. The Ultra system at Heathrow is like any other automated people mover with smaller cars and that 1970’s Sci Fi look. Lets see what happens once they have to have pods crossing intersections in the system or peaks of passengers or both.

More on light rail headways: Bordeaux runs trams every 4 minutes at rush hour, Lyon every 2-8 minutes, and Paris every 4-6 minutes. None of these light rail systems has any fancy underground infrastructure like in Seattle, or else it would be called Métro.

Alon, it may be *possible* in some limited circumstances to run less than 5 minutes, but it is usually disruptive, especially in car centric cities in the US. I’ll note that every city you mentioned is outside the US.

As an example, the Hiawatha line in Minnesota has been a huge success, but even at 5-7 minute frequencies there have been significant issues with car/bus traffic congestion caused by the preferred signaling for rail.

As for the Calgary system, it is my understanding that much of it is at grade but with an exclusive or semi-exclusive right of way.

But in any case, I wouldn’t suggest PRT as a replacement for rail Lyon, Paris, Calgary, or any other city where rail has been successful. My advocacy is for places where rail is not a good fit; e.g. in moderate-density cities where the car culture is pervasive and a rail system is likely to be both disruptive AND underutilized. There are plenty of cities where this applies (especially in the US). In those cities, PRT can serve as a transit “starter system”, getting people out of their cars and into transit, thereby reducing the car crunch and eventually making the area more friendly to other forms of transit.

In this sense, when viewed as a piece of the overall transit puzzle, I can’t understand why PRT is viewed so negatively. The fact that a few overzealous promoters have overstated claims should not invalidate the entire concept.

Calgary has exclusive rights-of-way for light rail outside downtown, in freight rail and freeway corridors. So do Jersey City, Portland, and Los Angeles. It runs light rail in a transit mall downtown in streetcar mode – again, just like Jersey City, Portland, and Los Angeles.

Calgary is also a low-density city that up until light rail opened was dominated by car culture. Its citywide population density is 1,435/km^2, the same as Houston and Dallas’s. It’s exactly the place that transit opponents would hold up as an example of a city where light rail could never work.

Besides, why does car culture make PRT such a good fit? The main rationale for car culture is that building a road is much cheaper than building a rail line. PRT negates this advantage; it can’t be used as a trunk line in an unwalkable suburb, which requires it to serve every cul-de-sac. You’d be getting the capacity of cars for the cost of building light rail everywhere.

Mike C.My advocacy is for places where rail is not a good fit; e.g. in moderate-density cities where the car culture is pervasive and a rail system is likely to be both disruptive AND underutilized.

But buses–with judicious use of transit priorities, such as selective signal priorities, intersection “queue jumpers” and short exclusive lanes in congested areas–would generally be far more cost-effective and quickly installed in places where low passenger volumes could never justify fixed guideway transit of any kind, such as a city of 30k with three small universities, like Winona, Minnesota, where the PRT hucksters want to set up a test track.

I’m glad to see that PRT advocates like MIke C have backed way off from some of the more outlandish claims made in the past by PRT boosters, such as capacities of 7,000+ pods per hour with half-second headways. I’m also happy to see that the more “reasonable” (a relative term) PRT advocates have also backed off and have agreed that the likely scope of PRT installations–if they ever get beyond Heathrow and Masdar–will be limited to special cases like “business parks.” But I still think his claims are way beyond what PRT can realistically achieve.

Never mind, in most potential cases where such PRT systems could in theory be installed, judicious placement of short new roadway segments for buses, along with major stop improvements, could provide very competitive service, usually at a capital costs an order of magnitude cheaper than a PRT system, and likely much lower operating expenses, too. But I digress.

MAX does 16 TPH per direction between Gateway and Rose Quarter, 20TPH across the Steel Bridge, and 12TPH between Beaverton and the Steel Bridge; much of this is at-grade. The Transit Mall does 8TPH + 180 busses per hour during rush hour.

Michael, please refrain from using derogatory terms like “hucksters” – that is a completely unfounded accusation. The Winona effort has support all the way up to the Minnesota state DOT.

What seems to be missing here is that PRT provides superior service, and would therefore (likely) draw more people onto transit. Sure a bus would be cheaper, but buses rarely draw more than a few percent out of their cars. In contrast, even PRT critics (e.g. the authors of the Cincinnatti OKI report, which rejected PRT in the 1990s) acknowledge that well conceived PRT system would draw a *much* larger percentage of car drivers. Most ridership studies estimate 10-30% could be drawn to transit from cars, compared to 1-2% for most bus systems.

The reason for this is the superior service: never having to wait more than a few minutes for a vehicle, no stops, no transfers, no standing, private travel, 24×7 availability. These features appeal to those raised in a car-dominated society.

So maybe Calgary had the foresight in the 1960s to restrict road building, limit downtown parking and set aside land for future LRT development. That has enabled them to be the exception to the rule in North America. But in most car centric US cities, that will NEVER fly, because these days people in those cities view personal on-demand transportation as a BIRTHRIGHT.

We can’t turn back time and undo the car culture in the dozens of cities where the automobile is entrenched. In these cities, PRT could provide a smooth transition to transit. For that, it should be supported by those who advocate more transit, not ridiculed.

There is much misunderstanding of PRT in the comments so far. I will address a few key points:
1. Capacity. The ULTra system as it is being installed at Heathrow has a theoretical capacity of 7,200 seats per hour. Using a more realistic two to three thousand passengers per hour you will find that the quoted $7M to $15M per mile of guideway is significantly less expensive than light rail. This is based on a three second headway (time between T-Pods). If headways come down to one second as expected, the capacity is trebled.
2. Passing. Stations are off-line (on sidings). If it is not your station you just go on by. All trips are non-stop. Light rail has a maximum speed of 55mph yet only averages about 20mph because of all the stops. A 25mph PRT system averages about 25mph.
3. Accessibility. PRT systems are laid out in networks, not corridors, so comparisons to line haul systems are not always appropriate. Networks cover large areas with numerous stations so PRT systems are available to more than just those living along the corridor. Network capacity can be very large even if individual guideway capacity is not.

Please visit http://www.prtconsulting.com to learn more about this technology. It is by far the most sustainable solution to urban public transit that is available today.

Mr. Mueller, there is NO misunderstanding of PRT here. This old, hoary claim of “misunderstanding” sounds exactly like Objectivists, Scientologists, hard core “Sarah Palinistas” and other cultists who claim people will convert to their beliefs once they are “understood.”

Based on what I have read over 30+ years starting in the mid-1970’s, I have very little faith, unlike you, apparently.

I also wish the more “reasonable” PRT advocates, and its huckers–see, I’m distinguishing here–would stop using the present tense when talking about PRT. Until there is some operating experience starting with Heathrow and possibly Masdar (it remains to be seen how the Dubai debacles impact Abu Dhabi), any claim about PRT is future tense, conditional on actual demonstrated performance.

If you want to discuss the various “human factors” I discuss in my latest post at Publictransit.us, I’m all ears. I’m particularly interested in how PRT advocates propose to solve the “Little Old Ladies in the PRT Station” and “Getting the Right Person to the Right Pod” problem when dozens of people are waiting around in a pod station during the peak hour. Or solve the problem of presenting very complex network information in a PRT network with more than a few stations to non-tech saavy humans.

In other words, solving the sorts of problems one would be aware of IF one has had decades of experience in actual transit operations (too many conventional systems fail at these seemingly simple tasks, or just muddle by. Without a human staff presence, they are potentially much more problematic).

Just to finish my thoughts here, PRT advocates are the ones who have to PROVE the viability of their concept, not me to “disprove” that it won’t work. Why can’t you take my extreme misgivings as a challenge, not as an insult (there has been plenty of name-calling on your side, too!)

In any case, the “proof” will result, if they materialize at all, from many years of trial and error with more complex networks than Heathrow, assuming that system works more or less as promised. Of couse if it does, I expect PRT to again be grossly over-hyped the way it has since the 1970s.

Mike, what do Calgary’s parking restrictions have to do with light rail capacity?

I find it ironic that PRT advocates swear theirs is the only system that can wean people off highways, but then use highway advocates’ arguments: American cities aren’t dense enough, Americans won’t accept public transit, the US is special, Americans were raised with cars. None of these arguments makes any sense – for example, Portlanders and Calgarians had been raised with cars in 1980, and neither Portland nor Calgary is a dense city – but they can be effective talking points when you repeat them over and over.

Now, you think American cities won’t commit to light rail. I think they will; when Utahns support higher property taxes to pay for Salt Lake City light rail 56-39, and when LA County votes 2-to-1 to tax itself to pay for rail improvements, I don’t think US cities lack in support for greater light rail investment. Apparently, all those people taxing themselves for transit don’t think on demand transportation is a birthright.

Finally, you ask why transit supporters ridicule PRT. I can’t speak for anyone else, but I do it because you’re bashing light rail using arguments that are factually wrong, and then advocating a $10 million/mile network spanning all streets as a replacement… you can see where this goes.

Alon, I have not bashed light rail in this thread, nor do I ever bash light rail. I only suggest that PRT may be a *better* option in *some* situations. It seems that it is you who are taking an extreme position here, asserting that PRT has no role whatsoever.

All I am suggesting is that there are *some* cities that would be better served by a PRT system, as opposed to a low-end light rail system that costs just as much (or more) and is bound to be underutilized due to the pervasiveness of the car culture in those cities. I further state that the existence of a PRT system in those cities may jump-start the transit market and reduce car usage, thereby making that formerly car-centric city more amenable to future transit expansion, including *rail*.

How is that bashing rail?

Is it because I quoted typical rail transit capacity figures in making the point that PRT is competitive with those systems? Is that what you call rail-bashing? Well, it’s not. I am simply making the point that “PRT is low capacity” is largely a fallacy when you compare both cost and capacity to existing rail systems.

We need to stop being so defensive about our “preferrred” transit mode, and realize that the true enemy here is the *automobile*. Any new technology that can make inroads into the car culture should be embraced by those who value transit and livable cities. And that includes PRT.

@Michael Setty wrote: “Just to finish my thoughts here, PRT advocates are the ones who have to PROVE the viability of their concept, not me to “disprove” that it won’t work.”

Then why are you so critical of trials that will go a long way toward providing that proof? If you demand proof of viability in the form of a real-world application, then you should support those efforts which will provide that proof, one way or another. Instead, you ridicule current efforts in Masdar, Heathrow, and Winona.

If you are truly confident that PRT will fail, then at the very least why not throw your support behind Masdar and Heathrow, two private efforts which cost us nothing but will provide valuable information on viability? If you are right on PRT, then these efforts will be utter failures, not a dime of public money will be lost, and you will be able to say “I told you so” to the world.

But what if they are *successful*? Would that be so bad, to have yet another transit weapon to use against the ever-expanding car culture? Isn’t that what we all want?

So, Michael, what exactly do we have to lose by backing Masdar and Heathrow?

This is the problem, Mike: you state things, often without evidence (has PRT ever led to interest in mass transit?). When we point out that what you state is incorrect, about train capacity and transit politics, you state the same thing again.

The word “extreme” in this context is a weasel word. It’s a slime tactic used by people who promote fringe ideas or gadgetbahn: bioengineering, maglev, automated electric cars.

The best concise description of this mentality comes from an article I read a few years ago about Thomas Friedman, who has boosted maglev, electric cars, and just about every other alternative to gas-powered cars that isn’t conventional mass transit. The article says, “There is, in fact, a Friedmanian dialectic. It only appears to go: thesis—antithesis—thesis!”

> Alon, I didn’t claim light rail is 1200, I said a bus or
> streetcar, which is a low-end rail system.

That’s what you have with buses, AND counting seat capacity only.

> When rail systems are at the street level, mixing with
> automobile/bus/pedestrian cross traffic, capacities are
> generally limited to no more than 5000-7000 max, because the
> traffic constraints restrict the frequency and train size. As an
> example, a 3-car train carrying 600 passengers and running at
> 6 minute frequency is 6000 passengers per hour. In most city
> applications, it would be difficult to run street level rail with
> larger trains than this, or at higher frequency, due to the
> limitations of operating on the street.

Huh? A streetcar/light rail train every minute is no big deal … in Switzerland, at least. The main segments in Zürich (Bahnhofstrasse, Quaibrücke) have 4 to 5 lines, all operating in 6 minute intervals (or even shorter) at rush hour. And in Basel, things are similar. And the total capacity of each train is (taking the official numbers of seats and standees) in the 350 to 400 people range.

Düsseldorf operates 75 m long trains (the legal maximum for streetcars in Germany), which would exceed your 600 person per train example, and there too, you find several lines operating at 6 minute intervals on the same segment.

One condition is, however, that there are no ticket sales and ticket checks upon entry of the trains.

> This is not to say that these systems don’t have merit, just that
> when comparing capacity to PRT, it should be an apples to
> apples comparison

And how much would PRT cost, which, because of automated operation would need a specifically protected right of way, which, if you operate at the 3 second intervals needed to get streetcar-level capacity, must be on another level, because it could not be crossed by anything (except suicidal rats ).

> The reason for this is the superior service: never having to wait
> more than a few minutes for a vehicle, no stops, no transfers, no
> standing, private travel, 24×7 availability. These features appeal
> to those raised in a car-dominated society.

Hmmm… so, PRT should be considered as replacement for the private car? Because, that’s what the above statement pretty much says. But then, what is the incentive to use PRT instead of my private car? Or a chauffeur-driven “private style” car (aka Taxi)?

The best-case scenario for hypothetical PRT is that it replaces private cars–and to answer Max, enables you to not own one, yet still live in the ‘burbs if that is where you want to live.

For that best-case scenario to become tractable, then the following must all occur:

* Installation of PRT becomes as cheap (or in the neighborhood) as installation of residential streets.
* Neighborhoods must be designed with it in mind.
* The community must have sufficient mass transit so that destinations that are longer-distance (and difficult to reach with a neighborhood PRT deployment) are likewise reachable without an automobile.
* Oh, gas gets really expensive; and the PRT becomes a more financially attractive option, even for commuters with fully-depreciated automobiles.

This is the best-case scenario, and I’m not sure that it is a very large niche.

But like I said above, PRT deployments–if and when the technology is ready–ought to be made on smaller scales. A neighborhood, for instance.

The next challenge for PRT makers and supporters of the mode: If and when a functional PRT system is built and becomes viable, how will it scale?

The problem with PRT businesses is that it is several companies attempting to enter deals to sell a bundle of proprietary solutions to the customer.

That right there ensures high costs. I doubt that PRT firms are going to agree to open-source design and technology standards. Right here is a dilemma: If the firms agree to open-source PRT standards, it becomes a commodity business where business must compete on price (lower profit margins) alone. In turn, a major construction firm can easily co-opt PRT design and offer it as a solution, blowing PRT specialists out of the water.

If the firms stick to proprietary technology, it keeps costs high and results highly variable. This in turn leads to no “knowledge tree” that engineers, suppliers and customers can turn to for solutions. Right here, PRT is already at a disadvantage since conventional transit system technologies both bus and rail have a forest of knowledge trees to compare costs and problems.

@Alon, I’ve made my points, you’ve responded with the standard anti-technology “gadgetbahn” smear. Clearly you’ve made up your mind, and there’s no point to further debate with you.

@Max: From what I understand, Zurich’s downtown area is almost exclusively trams, with little road traffic or buses to compete with. So, yes, you can run at higher frequencies in cities like that, which are much more common in Europe than in the US, where the car culture is pervasive.

It would be nice to transform our car centric cities into places like Zurich, but it’s exceedingly difficult to do that in practice, because it involves both physical AND cultural transformation, and both are disruptive. People used to the freedom of their car are fiercely resistant to transit which will affect their automobile mobility. Roads are already clogged, and the mere mention of converting lanes of car traffic to rail ROW is met with hostility. Even if projects can be launched, it takes months or years of construction-induced congestion just to get to the point where the cultural transformation can *begin*.

Once the lines are constructed, often times they don’t cover enough area to be useful, and even if they are people still choose the convenience of their cars to avoid what they view as the hassles of transit: schedules, transfers, and inconvenient stops.

So, when I earlier referred to the difficulties of operating at street level, I wasn’t referring to places like Zurich where transit is already established and the streets are largely devoid of cars, or Calgary where rail lines were well planned and the automobile expansion was actively limited.. These are the best transit cities in the world, but they are the exception rather than the rule, especially when considering cities in the US.

ULTra PRT guideway is very lightweight, therefore relatively inexpensive even when elevated.

So, at the high end, $30M per bidirectional mile for approximately ~1200-1500 passengers per hour in the short term, and if headways come down to 1s (likely), that triples to 3500-4500 per line. From what I’ve seen, this would be competitive on a cost-per-capacity basis with many light rail systems, which are generally in the 4000-6000 range for $30-60M (sometimes significantly more). For that cost, PRT would provide better service and likely lower operating costs.

PRT would also be non-disruptive, both physically and culturally. No sreet lanes would be consumed (not even during construction) so there’s little reason for opposition. Once constructed, it would provide a convenient, *car-like* alternative to driving, allowing the *cultural* transformation to happen naturally.

Of course, this is all speculation on my part, but it is not *unreasonable* speculation. There are very good reasons to assume that car-lovers would be more likely to accept a non-intrusive, convenient, car-like transit system. At the very least, the theory is compelling enough to *try*, don’t you think? At worst, you have a transit system that provides circulation as well as a streetcar would, for around the same cost.

I’m sorry you’re offended by the term “gadgetbahn,” but it’s no more offensive than to repeatedly say light rail’s capacity is “generally in the 4000-6000 range” when the actual capacity is 20,000.

And no, your evidence-free theory of why Americans don’t like light rail, except when they do, isn’t compelling to try. At this stage it’s like prayer studies. I don’t care that it’s technology; it’s ineffective technology. If you invent a Rube Goldberg device, don’t be surprised that people aren’t going to mass market it.

I’d second Wad’s point: The fundamental technologies of trains and busses are decades if not centuries old, and are all in the public domain. Some specific improvements may be proprietary, but the fundamental idea is readily available. There are many suppliers of rolling stock, infrastructure, design and construction services, and whatever else, for a transit authority to choose from–as Wad notes, it is a commodity market.

Something tells me, and I’m too lazy to go look it up, that the very concept of “PRT” is the subject of a gazillion patents and patents pending, and if such a system were to be deployed, the transit authority would be subject to massive vendor lock-in. (Which may well be one reason you haven’t seen it tried; it can’t be legally implemented without hiring specific vendors to do the work).

A related point, is that it seems that most PRT literature is marketed towards politicians and voters prior to sufficient demonstration of its viability. Most new technology is subject to intense academic and technical scrutiny, including by persons not involved in its development or promotion. To this end, the Heathrow project is a step forward. However, many of us consider the rampant promotion of the technology, especially in political contexts as opposed to professional contexts (including FUD-strewn pitches to the general public), prior to a successful at-scale demonstration of the technology to be a dubious endeavor. At best, your just trying to win business you have no business winning; at worst, you’re poisoning the well for technologies known to work today. This is a major concern in the US political context, where Promised Future Technologies (whatever their merits) are readily seized upon by anti-transit interests as a reason to delay roll-outs of planned mass transit systems, using existing technology. For the Randall O’Toole’s of the world, the mere idea of PRT, or long-range electric cars, or other many-years-from-efficient-production technologies becoming viable in the future, is advanced as Yet Another Reason why we should not build LRT or whatever now. But rest assured, if and when PRT is ready, O’Toole and his ilk will be against it, too.

As to the question of whether or not the “theory is compelling enough to try”–sure it is–if PRT advocates are footing the bill. You want to prove your point? Build one for free, or at least make such a compelling offer that a transit agency can afford to scrap it and start over if it doesn’t pan out. Or go secure grants for a pilot project through normal research funding channels. Or give Paul Allen a call–he loves to spend money on futuristic ventures like this. I’d love to see a trial. I just don’t want to pay for one.

Your argument basically boils down to “you can’t prove it won’t work, so you have no grounds for objection”, which is ridiculous on its face. Whether or not it is “worth the risk” depends on who is taking the risk. Your position seems to be that the risk should be borne by the public. It’s up to you to prove that it DOES work before aggressively seeking paying customers–it’s not the public’s job to be guinea pigs.

Mike C. sayeth:So, when I earlier referred to the difficulties of operating at street level, I wasn’t referring to places like Zurich where transit is already established and the streets are largely devoid of cars, or Calgary where rail lines were well planned and the automobile expansion was actively limited.. These are the best transit cities in the world, but they are the exception rather than the rule, especially when considering cities in the US.

So please explain why can’t we use Zurich and Calgary as role models given that their strategies for transit success are PROVEN, instead of a riverboat gamble on technology that has yet to be proven in service, as I’ve tried to point out through your thick skull all along?

The answer is that we can and we should. I’m not against the BAA experimenting with PRT in its own sandbox, perhaps someday producing a technology that MAY, or MAY NOT, have SOME applicability in niches where capacity more than an arterial lane of traffic or rapid service isn’t critical, e.g., other airports.

I rather be spreading the word about successful transit strategies than fighting half-baked pod schemes that detract from the important message from Zurich, Calgary and the few other places (even in Europe) that have truly successful transit.

Instead we get situations like Uppsala in Sweden which has been diverted so far by pipe dreams of Vectus pods, when they should be looking at Freiburg im Breisgau in Germany for a city in the same size range that has been spectacularly successful in transit AND alternative modes including bicycles.

Here is a link to the Freiburg im Breisgau tramway system, http://www.fr-strabbus-fan.de. If the bus battery technology I mentioned in my Winona, MN PRT Debunking paper works satisfactorily, the “ugly” overhead wires of tramways could be eliminated in many cases, particularly where they interfere with other wise attractive viewsheds.

Mike C wrote (#52): I further state that the existence of a PRT system in those cities may jump-start the transit market and reduce car usage, thereby making that formerly car-centric city more amenable to future transit expansion, including *rail*.

That’s an interesting point to consider, that PRT somehow would connect with mass transit. I’m picturing a light rail station being a transfer point to a PRT network. A bunch of pods waiting for passengers on several sidings. A train arrives and a bunch of people get off and head to the pods. Lines form at each siding of pods, and each person takes at least 15 seconds, if not a minute to get into the pod and program it appropriately. The lines might not even empty by the time the next train comes by. This sounds completely and utterly unworkable.

If it doesn’t connect with mass transit, then I rather doubt PRT riders would develop any sympathy for mass transit. In fact, they might more resemble drivers who want more of their kind of infrastructure — just PRT rather than roads.

#58: Roads are already clogged, and the mere mention of converting lanes of car traffic to rail ROW is met with hostility. … No [street] lanes would be consumed (not even during construction) so there’s little reason for opposition.”

So PRT not only can have 1 second average headways, but it also can take no space? What? And you are deluded if you think drivers will not object to space being taken away not just on one main corridor, but on an entire PRT network, and for some sci-fi pod cars, with their tax dollars.

Once the lines are constructed, often times they don’t cover enough area to be useful, and even if they are people still choose the convenience of their cars to avoid what they view as the hassles of transit: schedules, transfers, and inconvenient stops.

For riders, transit is not about area covered but about destinations covered. People are easily willing to walk 600-800m to get to a station with high-quality transit (simple, rapid, frequent, and comfortable). Moreover, high-quality transit alters the land use around it so that there is just more stuff around the stations or corridor. So talking about transit lines in general not covering enough area misses the land use impact of transit infrastructure and the broad geographical reach of good transit.

But that’s an interesting idea: assuming an urban system were built, PRT should be pretty good transit. More than that, it’s transit infrastructure, that no budget-limited municipality would ever build in more than a limited network. (If you can build less because people would be willing to walk to it, you will not be able to justify building more. Unlike roads, which need to get to every last house.) What this implies is that (somewhat scarce) PRT infrastructure will attract development around it, and it seems to me that this kind of success of a PRT system would lead to its collapse due to its fundamentally low capacity.

Transit infrastructure attracts development; if you can’t scale to handle the crowds, you’re doing it wrong.

@EngineerScotty: the main problem I have is with people who object even to the privately funded efforts. The top three active PRT systems are mostly privately funded (ULTra, Vectus, 2getthere), and the two initial target applications are private. Yet the anti-PRT crowd is highly critical of even these private efforts. Why is that? Why so much hostility towards Heathrow and Masdar if they’re the ones footing the bill?

Also, regarding proprietary PRT technology, there is certainly a proprietary aspect to many current systems, but the underlying theory is all well documented. A US government sponsored research project in the early 1970s laid down most of the theory and published it in a book, Fundamentals of Personal Rapid Transit. Others (primarily Ed Anderson) have published much since then.

I do agree the proprietary nature of individual PRT systems would need to be addressed, but I don’t think this is an insurmountable barrier. For example, cities which invest in a proprietary technology can protect themselves by including protective language in the contract which specifies the release of all system information if the company fails. The technology is simple enough that a third party could assume maintenance/expansion even if the original company fails.

“thick skull”, “half baked”, “gadgetbahn”, “pipe dreams” – this is the language that passes for debate here? If PRT is such a slam dunk failure, why do transit people feel the need to trash it with such over-the-top language? Why not just let it fail?

Michael Setty: why not let the Swedes implement their podcar systems, and if they fail miserably as you predict, PRT will be out of your hair and you can look like a genius? The amount being spent on these systems is a drop in the bucket relative to overall transit spending, and a few failed pilots in Sweden will not break the bank. But the knowledge gained from those tests will be invaluable, one way or the other? Why the resistance?

It’s almost as if some people *want* it to fail, and *fear* it will succeed. That’s the only explanation I can think of, to explain how *passionate* people are in opposing what is essentially just another transit mode.

Regarding your comment about space usage: PRT is elevated, on 3-foot diameter poles that are 50-feet apart. Stations are mostly elevated. The space occupied is therefore almost exclusively in the air and away from existing street traffic. This makes it fully compatible with existing street-level rights-of-way, including auto, bus, streetcar, or pedestrian.

Your further comments about PRT being “fundamentally low capacity” miss the point, because it’s not low capacity. PRT doesn’t match the capacity of a metro or exclusive-ROW light rail, but it does compete well with many street level light rail and bus systems, especially in the US.

I’m not hostile to Heathrow. At all. Other commenters here, maybe, but I’m glad to see a modern production PRT going online. (OTOH, I haven’t seen to many comments calling for Heathrow to scrap the project, most objections simply think the technology is not a practical solution to urban transit needs, which differ greatly from the people-moving needs of an airport–a facility where the distances are relatively short, there’s no need to condemn anything or worry about NIMBYs, and interference from traffic or pedestrians is not a concern).

And by privately funding, I don’t mean just funding of R&D and marketing and such–I mean private investors willing to fund a full-scale demonstration system. There seem to be plenty of deep pockets hoping to cash in, but they don’t seem to be interested in putting their money where their mouth is, and offering to build a trial system in some city somewhere (even in some place where a lot of the red tape that afflicts US transit buildouts can be done away with).

Could a transit authority spec a useful PRT system and hire a general contractor to build it, without violating some patent that isn’t freely licensed? Patents themselves aren’t bad in public works, if they can be implemented on a reasonable and non-discriminatory basis–but exclusive patents are avoided by wise transit authorities, unless their effects can be contained.

You can’t eat your cake and have it too. If it’s a fully elevated system with elevated stations, then it won’t come cheap. This sounds to me like heavy infrastructure, in sharp contrast with light rail.

“Your further comments about PRT being ‘fundamentally low capacity’ miss the point, because it’s not low capacity.”

Again, will people want to live and work near the thing or not? If not, then there’s no point in discussing urban PRT. If they will, then you must seriously consider whether it will be able to handle the capacity. In urban light rail, the demand is generally the limiting factor; it’s not hard to run more trains or longer ones. For PRT it’s the technology, and the limit that entails may be so low that reasonable land use impacts will suffocate it. If PRT is as awesome as claimed by proponents, then people will want to live and work near it; it’s clear that there would be PRT-oriented development. Instead of ditching the issue, advocates (and others) need to calculate the maximum density that PRT can support. And if it doesn’t even work in theory (with those unrealistic average headways), no Heathrow experiments will save the idea.

For PRT to have a chance, its cost per linear mile (design and construction costs, not ROW) has to be comparable to pavement. Not to metro systems or even LRT; pavement.

If you want a cheaper at-grade LRT that runs in its own right of way, either BRT or rapid streetcar have lower construction costs (but correspondingly lower maximum capacities and higher per-passenger operating costs), and peak capacities similar to what PRT seems to offer. And numerous functional examples of both can be found operating today. PRT will have a difficult time competing in this space. While LRT systems operate in this space (including a significant amount of trackage in Portland), other technologies handle lower-volume, lower-speed applications far more cheaply.

No, the killer app for PRT, if it is to have one in urban design, is probably not competing with trams or busses, but competing with autos. And for that to work, it has to be cost-effective with auto infrastructure. And while there might be case to be made there, considering the gazillions of dollars spent on autos and fuel, many of those costs are borne over time by end users, not up front by developers or government agencies. PRT, to succeed in this niche, will have to cost a heck of a lot less than $10 million per unidirectional linear mile.

By the way, I don’t really care what Heathrow or Masdar do. Those might be interesting experiments, sure. I care about urban transit and I don’t want to see places that badly need it (e.g. most of North America) make poor transit choices.

@Michael D, PRT guideway is NOT heavy infrastructure, it’s extremely lightweight. Guideways are significantly smaller than pedestrian crosswalks. Here is a the ULTra page which discusses guideways, including photos from Heathrow:

Stations are also small because service is on demand and there is no need for a platform to aggregate passengers. Stations are also more densely distributed than other forms of transit, further lessening the need for big stations.

This one is at-grade, but there would be little difference in the elevated version other than the addition of a stairway and small lift for accessibility.

You write: “Instead of ditching the issue, advocates (and others) need to calculate the maximum density that PRT can support. And if it doesn’t even work in theory (with those unrealistic average headways), no Heathrow experiments will save the idea.”

Those studies have been done, and ATS (makers of ULTra) is, in fact, targeting moderate-density cities where capacity would be manageable for the initial phases of the system, e.g. Santa Cruz, Mountain View, Daventry (UK). It’s not like ATS is going after the London Underground.

And might I suggest, that having so much demand that the system is overburdened is a *nice* problem to have? Because such high demand it would indicate that people are willing to accept this public transit system as an alternative to their beloved cars. If the over-capacity problem is that bad, then you can bump fares during heavy use periods, increasing revenue which can be used for system expansion. Alternatively, buses can run on the streets below to augment the PRT during the rush. Again, this is a nice problem to have.

And while PRT will not be able to serve the most dense areas (lower Manhattan is certainly not on the short list of applications for any sane PRT proponent), guideway density CAN be increased as needed, by building more guideway within an area already under service. The lightweight, non-disruptive infrastructure enables guideway penetration down to 1/4 mile spacing or less. Now, of course, this costs money, but if the system is so popular that demand exceeds capacity, it should be uncontroversial to invest in more PRT density, and the high fare revenues should help to offset the costs.

And of course, if the PRT is this successful, it opens the door to rail expansion, light or even heavy rail, that would have been much more difficult in an automobile-only environment. As I’ve said before, I think a successful PRT system can introduce transit to markets that have traditionally been resistant to any form of transit, and that can spur further rail development.

Warning: the following post contains hyperbole because it pleases the author to do so. Viewer discretion is advised.

Quite honestly, PRT is a bit much for this layman to swallow. The arguments presented here in favor of it appear to basically boil down to “magical robot cars will whisk us from place to place at the push of a button!” Color me unconvinced. (Mr Muller in comment 47 apparently pimping his financial interest doesn’t serve to sway me, either)

The initial “demonstration” project which Mr Freemark posted on is an incredibly circumscribed environment, where it won’t be competing with other transit modes. In that circumstance, it may well be a choice which gives superior service to other choices which could have been made.

But in a transit situation, it’s not going to compete with higher-capacity modes in denser areas (BTW, buses and streetcars are quite capable of passing unneeded stops; here in snowy Oslo, Norway, they just blow by empty stops if no rider has requested to get off. Incredible!), and in densities “too low to support” buses/etc, you’re solving the wrong problem: suburbs are built to service cars, not people, and that doesn’t change if you replace individually-owned cars with PRT or even magical flying ponies that fart ozone to replenish the hole over Antarctica.

Treat the disease, not the symptoms:

Zoning laws in much of the US mean that, even if you had 10,000 people lined up to live in a high-density neighborhood, you couldn’t build it. And developers are in it to make money, not fight city hall on the behalf of others, so they end up building within the established parameters, which means road access, acreage, height restrictions, etc; all of which essentially mandates low-density development with an existing automobile infrastructure.

Cheap petroleum means that it’s more economically attractive to use private cars than transit service (and a large amount of the US isn’t served by transit at all, or served poorly).

Ignoring your insult-filled tantrum, I have a specific question for you:

In your Winona paper, you claim that the absolute minimum PRT headway will be 5 seconds, and that it cannot go any lower. Now, I know you are aware of a system from 1978 called Cabintaxi which received full regulatory approval to carry passengers after several years of continuous system testing. Cabintaxi was approved at 2.5 seconds headway.

Michael, how do you account for this discrepancy? How could it be *impossible* for headways less than 5 seconds *today*, when Cabintaxi achieved safety approval at 2.5 seconds, *thirty* years ago?

Mike C: A central reason I don’t want to debate you anymore is because you have consistently misrepresented much of what I’ve said.

And why do you persist in attempting a “gotcha” argument strategy, including a nitpick about Vuchic’s rather detailed discussions and analysis of transit headways?

I think it’s because you don’t have the “proof in service” of PRT. As I pointed out before in this thread, Heathrow may, or may not, provide some evidence, but it will be many years if any more for larger and more complex systems is forthcoming.

And you persist in the misleading present tense about PRT, “e.g., PRT is blah, blah, blah, rather than the correct future conditional tense: “we think PRT can do X, Y, Z, and we think this will be proven in the next few years by Heathrow, Masdar, etc.”

For the record, I never denied that a minimum 2.5 second headway was approved for Cabintaxi nearly 40 years ago.

For the benefit of Yonah’s readers, here is the passage you’re talking about on pages 12-13 of my Winona paper:

[pull quote Wikipedia article on headways] In the case of automobile traffic, the key consideration in braking performance is the user’s reaction time.[6] Unlike the train case, the stopping distance is generally much shorter than the spotting distance. That means that the driver will be matching their speed to the vehicle in front before they reach it, eliminating the “brick-wall” effect.

Widely used numbers are that a car traveling at 60 mph will require about 225 feet to stop,[7] a distance it will cover just under 6 seconds. Nevertheless, highway travel often occurs with considerable safety with tip-to-tail headways on the order of 2 seconds. That’s because the user’s reaction time is about 1.5 seconds,[7] so 2 seconds allows for a slight overlap that makes up for any difference in braking performance between the two cars.

Various personal rapid transit systems in the 1970s, and more recent experiments in car trains and flocking, reduce the headways considerably. Under computer control, reaction times can be reduced to fractions of a second. Whether traditional headway regulations should apply to PRT and car train technology is debatable. In the case of the Cabinentaxi system developed in Germany, headways were set to 1.9 seconds because the developers were forced to adhere to the brick-wall criterion. In experiments they demonstrated headways on the order of half of a second.

Based on this, the author estimates a minimum practical [e.g., in day to day RELIABLE service] PRT headway of 4-5 seconds mainly to allow for flexible operations–vehicle entering and exiting PRT “mainlines” from off-line stations, switching, and so forth–but also to provide an adequate margin of safety., [emphasis added]. In the author’s opinion, most PRT advocates–very few of whom actually have “hands on” transit operating experience and are often ignorant of the myriad details required to maintain safe operations –don’t account for providing a sufficient “margin of error.” The Metrolink and Washington Metro train crashes proves the old maxim, Murphy’s Law: “Whatever can go wrong will go wrong.” While computers have dramatically improved reaction times compared to human drivers, mechanical braking systems still require actuation time, and some distance is still needed for vehicles to stop before crashing into one another. Unlike automobiles, PRT vehicles do not have seatbelts, thus braking rates must be gradual so PRT passengers are not thrown out of their seats.

————
One reason railroad signaling systems use two blocks to separate trains is redundancy and also for fail-safe safety. As I’ve also mentioned in my recent posts at Publictransit.us, the paper I quoted about the DIA baggage system operated with fewer delays at 30 baggage pallets per minute, rather than “at the limit” at 60 pallets per minute, e.g., 1 second headways.

If you don’t get this point, I can’t do anything else to explain it to you.

Forgive my if I remain unconvinced by your arguments citing two entirely unrelated systems in your analysis. You keep bringing up the railroads Denver baggage system as evidence, while apparently dismissing irrefutable data from an actual PRT system from the 1970s.

What you fail to understand is that increasing separations is not the only way to achieve redundancy and fail safety. PRT vehicles are engineered for aircraft-level reliability, meaning there is internal redundancy of all critical components related to safety.

So let’s say that PRT vehicles are engineered such that a stopped vehicle is detected in the follower within 50ms of the front vehicle stopping, and the brakes can be activated within 50ms after that. Further, let’s say the vehicle employs redundancy to ensure that there is less than a one in 10 million chance of failure in detection and/or braking.

This means that there is only a one in 10 million chance that the follower vehicle will NOT have its brakes engaged within 100 milliseconds of the fault in the leader. This is essentially a guarantee (within acceptable safety limits) that the follower will stop as long as the vehicle separation is just a little more than the stopping distance plus the distance traveled in the initial 100ms.

In other words, the redundancy is in the vehicle components themselves, and there’s no need for additional redundancy in the headway time. Railroads (and apparently the Denver baggage system) don’t have this kind of redundancy, and require longer headways as a result.

How can you imagine that their is no redundancy in railroad !!! Aircraft level safety is no better than railway level safety please …

I work in railroads and excuse me but 10 million chance of accident in a single brake action is not acceptable at all. We usually work on a level of an accident on one billion on the system life (30 years). And remember that there are still accidents !

I also confirm that safety team usually takes large safety margin to take into account unknown effects.

I doubt that a mechanical brake can activate in 50 ms. Remenber that a japanese team had to explore “explosive brake” to attain a specific performance …

Remember also that you cannot dimension your headway with the average time but you must use defensive values that are the worst possible. For example, this means that you must suppose that :
– the leader pod brake has brick wall stop because it is stuck for example
– the follower pod will break at minimum emergency brake power (or worst …)
– the reaction time is the maximum one thus counting all the different software cycle time that are used
– that the ground is slippery in case it has rain or snwoed
– etc …

Transportation is not a world of amateurs. You will transport babies and pregant women in quantities. Good will and hope is not enough. You have to be sure. Moreover, a single accident or incident can definitively stop all the system if a new danger is discovered too late.

By looking at the specs mentioned by Mike C. it shows that the guideway must be separated in any case; it is not really possible to cross the guideway (25 cm high kerbs can’t be used for “general public”). Therefore, even in the extremely lowest-density applications, you would have to build elevated structures… with a pillar every 18 meters.

OK, you could have your stop just in front of your front door, with according ramps, which would be some 60 meters long, in order to reach the “main guideway” (10 % grade, to get 5.4m clearance for road traffic … or 30 meters if you have the main guideway in your backyard and be able to walk underneath) (note these numbers are from the vendor’s website).

And, if you want to achieve a real private transportation equivalent, that would have to exist for every house…

The vehicles proposed for Heathrow look to me like fancy golf carts. So, where would you willingly ride a golf cart? Between a parking lot and the according building … and that’s just what we will see in Heathrow. Or in holiday resort complexes which are just a little bit too big to walk. Or in too big shopping malls, connecting some buildings.

But in suburban settlements??

There is a rule of thumb saying when transit can get successful, and to what you have to set up the capacity: 400 m to the next stop (which translates to 5 minutes easy walk). Actually, this is the guide value in the legislation for the Zürcher Verkehrsverbund. With a decent service, households can reduce to one single car without loss of mobility.

Would PRT fit into such a scenario? Maybe. Would the investment in a PRT system be worthwile for such a scenario (as compared to minibus-on-demand services? Barely, IMHO.

About headways: Some quick calculations reveal that, in order for a vehicle to safely squeeze into a continuous stream of vehicles, the minimum speed for 1-second headways would be about 50 km/h (about 14 m/s). And that would have to happen with quite high precision, and require ample accelleration space.

BLambert:
PRT isn’t meant to compete in highly dense areas (although some may believe it is, it wouldn’t be practical), that’s where some bus lines, LRT, and heavy rail would be the best options.
I agree that zoning in the US has historically been bad, but many places are working to change that. However, dependence on the car in inner suburbs is becoming more of a problem with congestion and sometimes lack of parking, but buses are impractical.

As much as I think transit is needed in more places, the densities are just not there to support it in most places in the US. As for buses, I think some corridors are great for buses, but as a network, they just won’t work to move people from cars or to help those that cannot drive or cannot afford a car. Buses (with the exception of those that use bus-only lanes) cannot provide efficient transit.

This is where I think PRT can be the best option. It needs some work, and I think Heathrow and Masdar can provide some insight, but the idea behind it for moving people is more reasonable in areas of congestion that can’t support rail. It would be interesting to see an experiment where they provide shuttles and PRT doing the same rounds at Heathrow and see how people use them and what their preference is.

Michael, re: PRT connecting to transit: this resembles the way some neighborhoods are served in Hong Kong and Singapore. In those cities, the subway network is not dense outside the central regions, and skips many neighborhoods and housing projects; instead, those neighborhoods are served by airport-style automated people movers, which are called light rail even though they’re technologically and operationally different from what is called LRT in the West. Those people movers aren’t PRT, but it’s conceivable something like PRT could be used for other areas not yet connected by people movers.

The main problem is that PRT doesn’t really work with high-traffic destinations, such as train stations, shopping centers, office buildings, and schools. Access and egress times are fairly high – I’m guessing on the order of 10-15 seconds – which means that the capacity of a single platform is about 300 people per hour. Even vehicle sharing couldn’t help much, because if you put 2 people in a vehicle side by side, then access and egress time would double unless you had doors open on both sides of the vehicle, which would increase station footprint.

Mike: I’m not sure why you think that American light rail cannot achieve full capacity because transit agencies are incompetent, but PRT would work well. Incompetence goes both ways.

@Max, you wrote: “the minimum speed for 1-second headways would be about 50 km/h ”

That’s not true. The ULTra vehicle is 3.7m, so “bumper to bumper” separation at 1-second headway would occur at 3.7m/s, or 13km/hr.

At ULTra’s vehicle speed of 40km/hr (11.1 m/s), the spacing between vehicles would be 7.4m (2 full vehicle lengths). When merging at these speeds and headways, the size of the “gap” will be 18.1m, or 5 full vehicle lengths.

The minimal acceleration space required can be calculated. Using 1.5m/s/s as the acceleration rate, the time to accelerate to 11.1 m/s is about 8s, and (using x=1/2 at*t for motion from a complete stop) the vehicle moves 48 meters in that time.

Regarding station capacity: a large capacity station will have more than one berth for PRT loading/unloading. In that case, the 15s load time per vehicle would occur simultaneously in N separate vehicles.

Further, ULTra’s station berths are arranged in a “sawtooth” form so that all vehicles have independent access to the exit guideway. This ensures that a single “slow loader” doesn’t back up the whole station, as would be the case with a simple linear arrangement.

So consider a station with 8 parallel berths and 20 second turnaround per berth. That equates to 8*3*60 = 1440 vehicles per hour. This platform would be about 4m*8 = 32m long. And the highly parallel nature of the ULTra platform means it could probably expanded to more berths if needed.

And I never said US transit agencies are incompetent, far from it. The US suffers because of cultural dominance of the automobile, which is the result of various social, political and economic factors over the past 100 years. Transit agencies were the victims of this centuries-long paradigm shift, not the cause.

Alon: Interesting argument about the high-traffic areas. However, in most instances, I still don’t think there would be a major problem. For one, if it was a bidirectional track, that increases your calculated capacity by a factor of 2. Boarding time could be decreased (for example if a bunch of pods were there, all were filled and left at the same time); also the system could be run so that the pod leaves and the destination can be picked after the pod leaves the station, limiting the wait as people try to figure out where they’re going.

For example, students from schools generally would most likely travel with friends or neighbors, and use the same spot, so more people in less time. Most offices would not have 300-600 or so people leave at any one time (if they did this in private cars it would be a nightmare). Transit stations are one place that could increase the footprint without it being a big deal, and a multitrack system could increase capacity, or major transit hubs could be on several different “lines” to different destinations.

That would mean, that a “siding” (access to a single house in the “suburban” scenario) would be about 100 meters long.

Hmm… that pretty much corresponds to the length of the ramps to and from a house for ground level access.

Hmm… that would give a minimum distance between individual house stops of something around 70 m (with some smart intertwining of the access ramps. Now, I wonder whether a suburban area with a distance of 70 m or more between houses would be willing to accept such a wall of access ramps. I don’t know…

One stupid question concerning the “sawtooth” or “parallel” berth idea: how are the passengers supposed to get to and from the berths? Assuming that the berths are not stub ends (which they aren’t, because of the term “exit gateway”), the “platforms” are insular platforms, and we have established before that the guideway can not be crossed by pedestrians because of the height of the guide bars.

Ahem…

Actually, it would be possible to have one long curbside, IF the vehicles are capable to operate without guide bars for a short distance, and with one single guide bar for a bit more. Such a stop would look like a bus bay.

Another aspect, I wonder how it will be solved in Heathrow, is the handling of empty vehicles.

Another aspect which must be taken into consideration for the calculation of capacity of any PRT is the number and distance of empty transfers, to or from the stop where a passenger got on or off. In the “suburban” scenario with its very unbalanced traffic pattern, this can be a considerable number (I guesstimate that around 40% of the movements would to be empty in the “suburban” scenario; at Heathrow, it could be a bit lower). Nevertheless, these movements must be taken into account.

For one, if it was a bidirectional track, that increases your calculated capacity by a factor of 2.

Could you explain this? I don’t see how bidirectional tracks double capacity. Do you mean having two tracks and two platforms? If so then yes, the capacity is 300 people per direction; the problem is that demand is often asymmetric. You can only really capacity per direction if you’re at a terminus, which may or may not be the case; this is equivalent to putting two platforms serving a direction.

Offices don’t have 300-600 people leaving at one time, but they do have 300-600 people leaving within an hour, which can be met even by automobiles on local streets. What cars can’t meet, PRT can’t, either: large schools need to accept or discharge 3,000 students within 20-30 minutes. City buses can meet this with multiple stations on multiple streets, and rail has the capacity for this, but PRT would have queuing nightmares.

Not all transit stations have enough footprint for the 10-20 platform tracks you’d need to meet peak capacity. About the only way I can see of making this work is dispersing demand, which means having PRT run alongside mass transit for 2-3 stops. For major destinations you’d have multiple stations for different sections – though even then PRT would have problems with track capacity, and multiple stations make more sense for large-footprint factories than for schools.

If it ever came to the point of having individual home access (something which I don’t believe is necessary or even desirable), there would likely be one low-speed siding serving the entire block of homes, with multiple entry/exit points. But I don’t think PRT needs to be that comprehensive. Successful transit cities with extensive rail networs have proven that a short walk to the station is acceptable for many riders.

And yes, the berths ARE stub-ends. The vehicles back out a few feet, then pull forward. See this for more info on ULTra stations. There are other PRT designs (e.g. Vectus, Taxi2000) which don’t feature sawtooth stations, mainly due to the fact that those systems have a more complicated track layout. In those systems, linear loading would generally be efficient, other than being susceptible to the occasional slow loading passenger.

Empty vehicles have been considered, and 30-40% is the generally accepted percentage of empty vehicles in a PRT system. PRT empty vehicle movement is exactly analogous to trains and buses making return trips with vehicles that are much less full than the original trip, typical of rush periods.

Yes, PRT designers generally envision a larger number of very small stations scattered about. One of the more promising porposals is to actually incorporate stations into buildings themselves, and then it truly does becomes something like a “horizontal elevator”. This would reduce costs and enhance service, and I would think that property owners would be eager to provide such a convenience to enhance the value of their property.

My point about long lines of parallel station berths was not that it would be the norm, but rather, that it would be possible if needed.

For the “600 people leaving within an hour” problem, consider a 5 berth station near the building. At 15-seconds turnaround, that’s 4*5*60 = 1200 veh/hr. A 5-berth station is about 75 feet long, which sounds like a lot until you consider that 600 people are no longer parking their cars near the building. 600 parking spaces is 13,200 linear feet of parking (at 22 ft/space). If even a dozen of those parking spaces can be reclaimed for PRT stations, that’s room for plenty of PRT berths to service the required load.

One more point about PRT guideway capacity: as the network expands, overall capacity expands with it. PRT’s ability to use the entire 2-dimensional network means that local surges in demand can be spread out over a larger area. For example, consider a concert venue with a 5000-person capacity. That venue could be served by a number of PRT stations around the perimeter of the venue, each of which can take riders out via a different route. With a dense PRT network, there are many possible routes from point A to point B, so those 5000 concert patrons might be cleared in significantly less than an hour even though no individual guideway segment carries more than 1500 vehicles/hr, because the routing system automatically disperses vehicles to alternate routes when the primary routes are full.

Mike C @57 said PRT would also be non-disruptive, both physically and culturally. No sreet lanes would be consumed (not even during construction) so there’s little reason for opposition.

What??? Having elevated roadways running down or beside suburban streets, in front of suburban houses, and there would be no opposition? You’ve got to be kidding. This would have the NIMBYs out with torches and pitchforks. Having cars sailing along where anyone can peer into your bedroom windows or over the fence into your yard…

And will the pylons be in the centre of the road (traffic obstacle, and certainly disruptive during construction) or alongside? If they are alongside, where exactly, and how is that achieved? By removing parking? blocking the path of litter/snow clearance vehicles? blocking sidewalks or bike paths? requiring utilities to be rerouted (under the assumption that the point load from these things is going to be higher than what a sewer can withstand)? or compulsory purchase of pockets of front gardens? And that’s not even thinking about the stations and access, which also require some sort of footprint.

For example, consider a concert venue with a 5000-person capacity. That venue could be served by a number of PRT stations around the perimeter of the venue, each of which can take riders out via a different route.

This doesn’t work, not when construction cost is $14-30 million for a two-track route mile; in that case, you could have a reasonably dense network, but it would be rare for a destination to be served by more than one station or maybe two. City buses can sometimes handle loads at concerts because the street is already there, and isn’t very expensive to build or maintain, so you could have multiple lines. But as soon as you hit light rail costs, you have to have the same economics as light rail.

Geoff @79 said Buses (with the exception of those that use bus-only lanes) cannot provide efficient transit.
I’m not sure what the rationale behind that is. One of my local routes in London has appx 240 buses per day, the majority of them articulated buses. With stretches of bus lanes, it’s not far off car speeds in the centre of town. It’s about 3 min headways at peak, so if I want to finish a cigarette or wait for a less crowded bus, I’ll just let it go by and catch the next one. (OK, yes, it is one of the most frequent bus routes in London, but it’s one of a number of routes that will get me home. There are also much less dense areas served by regular services.) The point is, the London buses network is bloody efficient at moving people around – some 6 million boardings every weekday – at various densities from the centre to the suburban outskirts.

The guideways and stations would not necessarily serve only that venue. What I was suggesting is that the larger the network gets (in both area and density), the greater the capacity to overcome local surges. So in my example I said stations would be located around the perimeter of the venue, but they would also serve adjacent buildings, and there would have guideways going off in different directions to cover different areas.

Think of a 2-dimensional grid with the concert venue at some point within that grid. At a minimum, there would likely be 2-4 guideway paths away from the venue as part of the overall network layout. These can be used in parallel to multiply traffic out of the venue. Once out of the congested area immediately surrounding the venue, vehicles can be routed efficiently down the least congested path towards their destination.

Since a concert venue is a known aggregator of potential passengers, the overall layout can be optimized to have several guideway loops converge at or near the venue, even as the primary purpose of those loops is to serve surrounding areas.

As for costs, I frankly don’t understand why PRT turns many transit activists into fiscal conservatives. Yes, the system is expensive, but so is rail, and transit activists don’t generally object to well-conceived rail projects. PRT is expensive to build but it would provide a valuable service to the community, like any transit. And if it is heavily used by a large percentage of the public, capital costs for expansion will be less controversial. I can’t remember the last time I heard a public outcry over road expansion/maintenance costs in my car-dominated city, because people view roads as a vital service. I think the same will be true of a well-conceived PRT system if a significant percentage of the public embraces it — and I think they will once they see the high level of service it provides.

@John W: I acknowledge that the NIMBY argument may carry some weight. People don’t seem to like the thought of elevated guideways, because it’s something different and unknown. The automobile-induced blight on our cities is “the devil we know”, so we don’t even notice it anymore. Huge intersections clogged with cars, traffic signals dangling on the horizon, monstrous density-destroying parking lots and parking garages scattered about, ugly fuel stations on every other corner, formerly walkable neighborhoods bisected by busy arterial routes or (worse) expressways.

Those of us in car-centric cities have come to accept all this as normal, but I think it has seriously degraded the quality of life in cities. So when faced with the prospect of a lightweight elevated guideway, I do consider the NIMBY/aesthetic concern of the guideway, but only in the context of the problems it can help solve. Will that PRT guideway alleviate congestion on streets? Will it provide an alternative mode that will reduce the need for more road expansion? Will it reduce the need for more density-destroying parking lots? And, more personally, will it give me a viable transit option which I can use to get to the places I want to go without using an automobile?

In my view, a mature PRT system will go a long way to resolving a lot of these issues we take for granted, and for that, a slim elevated guideway is a small price to pay. But I do acknowledge that I may be in the minority in that view; many people share your NIMBY concerns and that would need to be addressed.

ATS (ULTra) is, in fact, studying these issues. They recently held a design competition for a hypothetical PRT in the historic city of Bath. The purpose of this exercise was to come up with innovative ways of integrating PRT infrastructure in even the most sensitive aesthetic environments. I think more of this research needs to be done, and I think it will be productive, because PRT infrastructure light and flexible enough that it can be integrated with little disruption. Good design could never overcome the blight of an elevated automobile expressway, which is far too big to be integrated, but it could work on PRT guideways that are significantly smaller than a pedestrian crosswalk.

Mike C wrote: “And might I suggest, that having so much demand that the system is overburdened is a *nice* problem to have?”

It’s only a nice problem if you can fix it. PRT cannot be converted to any higher-order transit, by design. Even BRT has difficulties with conversion to rail — just look at Ottawa — and that’s at least a similar transit design.

“Think of a 2-dimensional grid with the concert venue at some point within that grid. At a minimum, there would likely be 2-4 guideway paths away from the venue as part of the overall network layout.”

Elevated guideway, elevated stations — and so many of both that there would be 2-4 (likely bi-directional) guideways to be found in the vicinity of one block? And you think this is somehow economically rational? I’m not buying it, and neither will reasonable governments. Governments cannot afford to spend that kind of money on low-density areas.

“Yes, the system is expensive, but so is rail, and transit activists don’t generally object to well-conceived rail projects. … I can’t remember the last time I heard a public outcry over road expansion/maintenance costs in my car-dominated city, because people view roads as a vital service.”

Costs are okay when they come with benefits to match. The costs of PRT per mile are on par with transit that has ten times the capacity. Considering that public transit requires a subsidy, just as do roads, it is unacceptable to spend limited tax dollars on low-benefit, high-cost projects — bridges to nowhere. And yes, roads do cost a hell of a lot of money — but even those costs are an order of magnitude or two lower than PRT per trip served. Good transit projects, on the other hand, cost substantially less than does equivalent road expansion.

Mike C, #78This means that there is only a one in 10 million chance that the follower vehicle will NOT have its brakes engaged within 100 milliseconds of the fault in the leader.

But the chances of programmer error in some part of such complex software is one in one. I’ll stick with physical redundancy, fail safe operations and safety, thank you.

Also, EXACTLY what do you mean by 1 in 10 million chance of failure. Is this per computer calculation or something else? You’re a programmer; please explain in plain English so the non-programmers here can understand what you’re saying.

Michael: a 1 in 10 million chance of failure means that some hack multiplied probabilities together so that management would not be found liable for the Challenger disaster.

Mike: you keep touting those dense networks of $15-30 million/mile routes (not including multi-berth stations), such that every secondary destination gets multiple lines. Where is the money going to come from?

Yes, Alon, the track record for the Shuttle program is 1.55% failure so far, based on two disasters and 129 missions through July 2009. I think they’re retiring the program because NASA accepts the fact that a 3rd Shuttle disaster is inevitable.

I also know that the chance of Word crashing, even on a Mac (which has an extremely stable OS) is one in one from “out of memory” errors (I think this is “memory leak” in programmer-eese) if I leave Word open for more than 24 hours. The current Mac version of Word is much better than before, but it still sucks relative to virtually all other Mac software.

Have either of you taken a flight recently? I assume not, because clearly you don’t trust the software designers and reliability hacks who designed the systems that enable safe air travel.

Seriously, reliability engineering is a well established science. It’s the reason why individual component failures can occur in a jet flying at 30,000 ft, without catastrophic results. Do you think the safety of air travel is a fluke? The engineering required to reliably keep a multi-ton metal tube floating literally in thin air is extensive, and it must also be exceedingly reliable.

I would guess that a PRT vehicle has one one-thousandth the inherent complexity of a commercial airliner, yet you are skeptical that it can be made reliable enough to apply a simple mechanical brake. Meanwhile, you board planes without thinking twice. How does that mesh?

Or maybe you don’t fly, in which case I can fully understand your distrust of PRT reliability.

OK, so now you’re comparing PRT to attaching a reusable vehicle to several tons of liquid explosives, launching it into orbit, then returning it safely home? And this is supposed to predict the reliability of operating golf carts at 25mph on an exclusive guideway?

And I wasn’t directly comparing automated golf carts with Shuttles. You misrepresent what I said, again. Ho-hum.

On the other hand, a PRT system as a whole probably would be comparable in complexity to a Shuttle. Of course, I doubt you or any other PRTista has any clue where that point of complexity is. Clearly, the Heathrow PRT is at the low end of the evolving PRT complexity scale, and they’re still have major teething problems that recently led to a nearly year long delay.

Also, are you saying YOU have a thorough understanding of reliability engineering? Sounds like it. Am I supposed to take your vast knowledge of aircraft reliability engineering on faith? Oh, wait. I’m also to have “faith” in the very low infallibility of PRT technology.

Mike, I fly with the knowledge of decades’ worth of statistics about failure rates. There’s no guessing there; the numbers are empirical. In the 1930s, the numbers were empirical, too – they did extensive testing, in which many pilots died, to make sure flying was safe for passengers.

Alon, you beat me to the last comment I left out; e.g., that the latest, most complex jumbo jets have also had the benefit of 106 years of airplane flight testing and myriad other efforts since the Wright Brothers. In contrast, the history of PRT and AGT is rather sporadic in comparison.

Michael, it’s basic reliability engineering. If you don’t know what that is, you can start your research here.

As for the specifics of ULTra reliability, why don’t you ask the regulatory authorities at HMRIwho have accepted ULTra’s design? When you’re finished there, you might want to contact the Swedish regulators who are working on the Vectus approval. Finally, you can contact the German regulators from 1978 who approved Cabinentaxi for passenger travel at 2.5 seconds headway.

Do you not trust these respected regulatory authorities to judge the reliability of a public transport system?

Also, following up on an earlier point, do you really believe that the reliability of the space shuttle has any applicability whatsoever to moving small vehicles at low speeds on a fixed guideway?

@Michael Setty wrote “On the other hand, a PRT system as a whole probably would be comparable in complexity to a Shuttle.”

Michael, the most complex PRT system is a tiny fraction of the complexity of the space shuttle. PRT is not rocket science — literally!

ULTra PRT is basically a golf cart on a guideway with a magnetic tracking system and obstacle detection. The central control is little more than simple linear trajectory calculations (which have been automated since the days of ENIAC) coupled with some routing and scheduling. From a pure functional perspective, that’s it. The role of the PRT engineer is to make this handful of simple functionality reliable, and judging by the regulatory acceptance of several designs, they’ve succeeded.

The fact that you believe a PRT network would be anywhere near as complex as the space shuttle reveals your fundamental lack of knowledge on the concept.

Any PRTistas here know what the projections are for miles or km between roadcalls being predicted by any of the PRT systems under development?

If a bus system keeps this measure above 10,000 miles between roadcalls, they’re doing reasonably well. Buses are relatively simple, of course, but they still do break down, and there is a long empirical record of why and how.

Hmm. I read the whole thread (more fool me). I notice that some people on this thread have been making definite statements to the effect that PRT cannot possibly work in any of a wide range of situations, and they’re making these statements with great assurance. Yet, these people base at least some of their statements on arithmetic that is easily shown to be faulty, or on “facts” that are easily checked and shown to be false. This does not inspire confidence in their conclusions.

I also notice that some people on this thread are very friendly towards trains and buses. I’m afraid I cannot share your enthusiasm for those modes of transport. I’ve waited on too many rainy suburban platforms, and crowded into too many sweaty, noisily rattling metro cars to be romantic about trains – except maybe the Shinkansen. As for buses, I simply hate them. They are grim, uncomfortable, and very slow. (A 30 mph operating speed on expensively reserved lanes is pretty meaningless when the vehicle is stopping three or four times a mile.) On a bicycle, I can always beat the bus in my city, and often by a wide margin. In fact, I can walk to the local “activity center” quicker than the bus, on average, could get me there, and I live near one of the highest-frequency routes. I find it unbelievable that some people, including some city planners, think the future of the city is bus so-called-rapid transit. That’s not a future I would welcome.

I hope Mike C is wrong about PRT, but only in this sense: I hope he is being too reasonable, and in fact the more ambitious claims made by some PRT proponents turn out to be correct. Then buses and suburban rail will swiftly be wiped from the face of the Earth, and private car use will simultaneously dramatically be reduced, and we will enter a new transport Eutopia.

Bruce, you’ve done more to marginalize your position than even Mike C. That’s quite an accomplishment.

PRT proponents have struggled to build a viable working model. The question is not the computing capabilities required to fulfill PRT designers’ wishes.

There are a host of real-world operational issues involved that are beyond the scope of solving by silicon chips.

Setty brings up a very good point about maintenance. What will be the forecast of road calls? More importantly, who will be responsible for them? Also, what is the schedule for routine/preventive and major overhaul fixes? Where are the parts’ sources?

There’s also the issue of operational costs. What is the funding plan to keep the pods and guideways running? Ignore the fact that there is theoretical savings from not needing drivers. Look at the costs that are there. What will pay for PRT’s power source? What about the cleaning and maintenance workers? Better yet, what is the revenue source? Fares? Even the most efficiently run systems operate at massive losses. PRT’s “fuel” cannot be taxed. Or will it be like a sidewalk, which has a farebox recovery of 0%?

What about system redundancies in the event of service failure? What’s the backup power? What are the alternatives available should all or significant parts of the system be out of commission? Bruce, we’d look like asses if PRT make mass transit obsolete — until the point comes when we need obsolete technology to rescue riders from a major service disruption.

@Michael Setty wrote: “Any PRTistas here know what the projections are for miles or km between roadcalls being predicted by any of the PRT systems under development?”

Well, not sure about PRT, but I do know that the space shuttle travels many millions of miles between “roadcalls”, and we all know how you tend to use space shuttle numbers to predict PRT reliability.

:-)

Serious answer: no, this “PRTista” doesn’t know (I love how the name-calling never ceases from the anti-PRT crowd :-)), but ATS does indicate that they have devised a regular vehicle preventative maintenance plan. Perhaps you should ask them.

A more important question concerning vehicle reliability–what happens when one does break down? If there’s a “grid” topology, it theoretically can be routed around, but a linear route would be shut down by such a happenstance, would it not? A bus breaking down doesn’t take out the entire bus system; a train breaking down on a properly dual-tracked line can be routed around (in worst case, a broken down train can be bridged with busses if routing around it is not possible).

“Bruce, you’ve done more to marginalize your position than even Mike C.”

I’m not interested in whether my position is marginal, or orthodox or not. Never have been. However, I will say that my attitude to trains and buses is very widespread — to the extent that those who take the opposite view are the unusual ones.

“Bruce, we’d look like asses if PRT make mass transit obsolete — until the point comes when we need obsolete technology to rescue riders from a major service disruption.”

That’s a hilarious statement, in light of my experience of public transport. I live in the UK. Trains here are regularly disrupted, sometimes by technical faults, sometimes by “planned maintenance”, and sometimes be industrial disputes. Then buses are used to provide a replacement service. Buses, too, are prone to being disrupted by industrial disputes. Given the proven unreliability of these services, it is a joke to say that they will be needed to step in as back-up for a system whose unreliability is not yet proven.

@BLambert:

“I don’t like transit, so I want a car to take me where I want to go.”

No, I don’t want a car to take me everywhere. I find driving mostly a boring activity. A year after I bought my first car, a colleague asked me why I always walked to work (a trip which took half an hour). Cycling I enjoy. I’d like safe cycle lanes, and I think covered cycle-ways would do more for green transport than suburban trains or buses ever could.

That said, if PRT works as well as it is theorized that it could, I would much prefer to ride the PRT than a train or bus. My reasons for disliking buses and not much liking trains are well-founded and widely shared. PRT is transit – it moves people around, and it is shared by the riding public. If I like it, then I don’t dislike transit as such, though perhaps I dislike mass transit. And why should I not? Noisy, crowded vehicles in which one is often forced to stand squashed like a sardine, shockingly slow travel, long wait times, service inconveniently discontinued at night and sparse on weekends – what not to dislike about mass transit? They are at best to be stoically tolerated.

I have no problem with fast, smooth, clean, comfortable, always-seated trains with reasonably low interior noise, such as the TGV and the Shinkansen, and I sort of understand people who want to ride unusual and very old historical trains, but to like these forms of travel in general – to find anything at all to love in commuter rail, metro rail, city buses – what kind of weirdo does that?

If a better system can replace them, well, hooray. Why should I care if some people think PRT is not transit? It promises quickness, convenience and comfort, and all at a considerably lower cost than trains. That’s what matters to me.

@EngineerScotty:

“A bus breaking down doesn’t take out the entire bus system; a train breaking down on a properly dual-tracked line can be routed around (in worst case, a broken down train can be bridged with busses if routing around it is not possible).”

In my experience, a broken-down train generally shuts down an entire line for anything from a few minutes to a couple of hours. A broken-down bus is not such a serious problem, but roads can become gridlocked for all sorts of reasons, and this does affect buses.

Obviously, PRT designers have thought about the problem of broken-down vehicles, and have proposed measures to deal with that problem. And obviously, since you’re an engineer, Scotty, and you’re interested enough in this topic to be posting here, you’ve read that one of their suggestions is to design things so that any working vehicle can be employed to push a broken-down vehicle to the nearest station. That seems like a reasonable solution which would prevent a widespread service disruption from occurring in most breakdown situations.

I said nothing about driving a car, I said you want a car to *take you* where you want to go. You don’t like mass transit because, horror of horrors, it’s loud and it’s got people in it? That describes cities, too, so maybe you’d be more comfortable not living in one.

I’m not interested in whether my position is marginal, or orthodox or not. Never have been. However, I will say that my attitude to trains and buses is very widespread — to the extent that those who take the opposite view are the unusual ones.

Bruce, your position isn’t widespread, except maybe among suburban NIMBYs and oil industry shills. Across the Sunbelt, cities are voting to tax themselves to improve bus and train service; in LA County, the margin was 2 to 1. It’s not very useful when you complain about facts that are “easily checked and shown to be false” without actually showing why they’re false.

And I’m glad you’re not interested in what effect you’re self-marginalizing. But that raises the question of why you’re writing comments in the first place. Is it just to tell everyone how great you are that you don’t like waiting on subway platforms? Or is it to tell everyone that you’re smart enough to know that the original spelling of utopia was eutopia?

How do you evacuate from one of these things if you’re stranded in the air halfway between two pylons? With no guardrail, the side door seems to be out of the question. It’d be like getting stuck on a ski lift.

That’s assuming there’s no one to give you a push. Or what if that won’t work, say if the car becomes jammed? (eg fallen tree branch wedged into the track). Big cranes to lift out the cars?

Re reliabiliity: Here is ATS’s discussion of reliability and how to handle vehicle breakdowns.

Short answer: the vehicles are engineered to very high reliability, with automated vehicle health monitoring systems to trigger maintenance on issues before they become severe enough to cause an outage. In the rare event of a breakdown on the guideway, they have procedures in place to handle it.

Why is this so difficult for some to accept? Do people here really believe that ULTra could have gotten regulatory approval without demonstrating vehicle reliability and contingency plans? Again, ULTra was designed to aircraft-level reliability standards; how many people here worry about planes suddenly dropping out of the sky?

I’ve been involved in online PRT debates for years now, and it’s always the same: people who’ve never even read a single page on PRT suddenly think they’ve found the “killer fault” that invalidates the entire concept, despite the fact that many very intelligent people have been working on this for decades and have analyzed to death every conceivable scenario.

And I want to stress again: regulatory agencies have approved PRT for carrying passengers. So those here who think it’s up to the “PRTistas” to prove safety and reliability have it backwards. Regulatory approval is a daunting and comprehensive task for a public transit system, and it covers all the issues raised here and dozens more. So for those who distrust the regulators findings, the burden of proof is on you to find where they went wrong.

I’m with Bruce. People don’t ride buses for a reason. The more successful transit is, the more unbearable it becomes. It only takes one crazy or inconsiderate person on the vehicle to make everyone miserable. I suspect that a large share of suicides happen in transit stations for a reason, whereas the pleasant sidewalks are merely venues for vehicular manslaughter. I think the mode share of transit in every metro area says it all. Only in NYC has the mode gotten much tranction in the US, probably because we’re so dang rich we can afford more comfortable transport.

To the naysayers, remember that our current public transit system is looking pretty broken at the moment:
– farebox recovery stinks
– mode share stinks
– there’s not enough money for operating subsidies
– new buses, vehicles, and fixed guideway are stupidly expensive
– there’s no private sector interest in investment in transit
– many American cities don’t have a good structure to support traditional liner route transit
– our fiscal outlook is bleak (see the total US governments debts figures that tally federal, state, and local debt – it’s not pretty and we look a lot more like Japan than the federal figures would suggest. Add private debt and you’ll have a panic attack. Then relax and remove a couple of points of GDP growth.)
PRT looks like the best bet to attract new private investment in public transit to help address congestion and mobility. City buses are a close second, but the services that have reasonable cost recovery aren’t the ones most people would consider riding because of comfort or convenience. And Phoenix is not and will never be London. There isn’t a block in Phoenix where 3 minute artic headways makes sense.

I think the peaking is an interesting problem in the system. To some extent, people compensate by raising the load factor in the cars and finding riding buddies to split their fare. Peak hour fares could also help move demand to the shoulders, and a PRT system could be dynamically priced or at least have fairly high quality demand-based pricing. I think having a guideway sturdy enough to run a distribution of vehicle sizes makes terrific sense, so long as this doesn’t impact costs too adversely. I’d be curious to see the cost curve, both to California seismic standards and to regular standards based on various maximum vehicle sizes. For an office complex, shuttle van sized vehicles would be a good match. Downside is that this would likely require more elaborate station design, but perhaps there are creative solutions (as always in engineering).

I wonder what sort of station concepts are out there to deal with peak demand. To me, that’s still the sticking point for many of these systems. Several ideas come to mind: passing the in the station to prevent queuing (involves more elaborate station or vehicle design), elevator type grouping pod assignment to increase load factors (I know a couple elevator companies are interested in this).

I think the multiple points of service would only make sense for the largest convention centers and stadiums, but most of the problem could be solved by properly sizing the platform length.

The private sector has some participation in bus. This participation is mainly limited to shuttle buses to and from rapid transit stations. It also includes assorted other shuttle buses. The remaining private participation is as a subsidized operator. Veolia et al typically run the service, turn over fares to the transit agency, and receive their revenue based on meeting their performance criteria. This contractor relationship does not constitute “investment” per se. The last example is of toll roads and HOT lanes where the concessionee runs a bus service or provides a fixed guideway as part of their contract to build/operate the toll facility. Again, a pretty limited investment.

The private sector has much more limited participation in rail. Mostly, this participation comes at the station level – redevelopment partnerships where the developer improve the station or more often the parking supply for the station in exchange for development rights. Value capture financing is a form of soft private participation. Both of these elements are pretty weak and do not go very far towards footing the bill for grade-separated rail.

On the other hand, people movers have seen substantial private sector influence. PRT in my view is just the next logical step beyond a people mover. Very similar technology with a further degree of complexity. As far as I can tell, it allows for a plug and play approach where a new investor will pay for an extension loop on the network as a real estate enhancement. In some place like Silicon Valley, this market is potentially quite large. The incremental investment for each loop is more modest, too. And a unsubsidized capital investment that is then turned over to a transit authority would thankfully skip a lot of state and federal red tape – every thing from Davis Bacon requirements to prolonged environmental review. The cost basis is looking pretty favorable. In the mean time, it would provide a much better experience to the customer than traditional transit, which most people just don’t want to pay for (yes, even those who do).

Transit is like tofu. Sure some people eat it because they like it, but in the aggregate, we all prefer pork, or lamb, or beef, or even frickin’ chicken. You can keep telling me it’s terrible for my heart, the planet, etc… But it tastes better, and I’d rather engineer a solution to keep the habit than to eat your tofu. Because tofu just isn’t that good.

ULTra was designed to aircraft-level reliability standards; how many people here worry about planes suddenly dropping out of the sky?

But no transit system yet has run to “aircraft level reliability standards” so I guess we’ll see if this works “on the ground.” As stated in the 1978 PRT book, this sort of reliability standard ALSO required a DAILY inspection of each vehicle, which won’t be too hard with only 18 ULTra vehicles, but a major logistical mobilization every day with hundreds or thousands of podcars in a system’s fleet.

You’ll also notice that any reliable airline also has a significant percentage of its airplanes out of service for maintenance and inspections every day.

Also, MIke C, many of us who allegedly “don’t understand” PRT just don’t accept all the claims made in the tons of reading material available on PRT since the early 1970’s. On the topic, “We’re from Missouri: Show Me.” Why don’t YOU seem to understand THIS POINT?

Veolia? JR? Japanese private railroads? MTR? MRT? Detroit light rail? Tel Aviv subway? Channel Tunnel? Desert Xpress? Each of those has private sector investment higher than the Winona or Morgantown projects. That there’s more private investment in PTR than public doesn’t mean much – the overall numbers are low; it’s just that the public sector is even more loathe to invest in PRT than the private sector.

And a unsubsidized capital investment that is then turned over to a transit authority would thankfully skip a lot of state and federal red tape

This is not true. Desert Xpress, a privately funded scheme, has to contend with the same environmental review process as public schemes like California HSR.

Private participation is not the same as investment. Investment is money that otherwise wouldn’t enter the pool. As a share of metro transit investment, private investment is minutely small in the U.S. Tel Aviv provides a great example of a successful PPP, but the subsidy is still comparable to examples in the U.S., and this kind of PPP wouldn’t be possible in the U.S. because of greater regulatory risk.

FTA funding comes with many strings attached and involves strict oversight from the MPO or transit agency. An FTA audit is not a pleasant process for a reason. Try meeting all the contracting, accounting, and outreach efforts to receive this money. This is one reason why the U.S. lags so many countries in delivering timely, under budget transit projects. In the case of California, the environmental review process is particularly strict. A 100% privately funded project in say Georgia would have a much easier time in review and planning and cost than a California publicly funded one.

I think it is foolish to dismiss an idea out of hand, especially when the status quo can best be described as a failure. The U.S. needs more private investment in metro infrastructure, and for the most part, this won’t come in the bus or metro rail sectors.

“I said nothing about driving a car, I said you want a car to *take you* where you want to go. You don’t like mass transit because, horror of horrors, it’s loud and it’s got people in it?”

Er, no. I enumerated my reasons for not liking mass transit, and the mere presence of other people was not one of those reasons. I highlighted the slow trip times, the uncomfortable, very noisy ride (almost deafening, in the case of most metro train services), the crush-capacity crowding which makes New Year’s eve on Trafalgar Square look sparse, and the inconvenience of waiting. So, you’re attacking a straw man of your own manufacture.

“That describes cities, too, so maybe you’d be more comfortable not living in one.”

As a matter of fact, surveys have found that people who live in big cities are on average quite miserable compared to people who live in small towns, leafy suburbs and rural districts. I don’t doubt that commuting by mass transit is a contributory factor.

@Alon Levy:

“Bruce, your position isn’t widespread”

My view is very widespread. The overwhelming majority of people in developed countries use public transport rarely or not at all, and indeed spend thousands of pounds to avoid doing so (i.e., buying, insuring, parking, fuelling and maintaining a car). Even in Japan, where the trains are famously efficient and punctual, the majority of journeys are not by public transport.

“It’s not very useful when you complain about facts that are “easily checked and shown to be false” without actually showing why they’re false.”

Others have already done so. I do not need to duplicate their work.

“But that raises the question of why you’re writing comments in the first place.”

(a) Because I have an opinion that is on topic, and (b) because I noticed some bad arguments, and bad arguments deserve criticism.

“original spelling of utopia was eutopia?”

“Eutopia” is not simply an old spelling of “Utopia”. The meaning is different. “Eutopia” means “good place”, whereas “Utopia” means “nowhere place”.

@John W

“How do you evacuate from one of these things if you’re stranded in the air halfway between two pylons? With no guardrail, the side door seems to be out of the question.”

This is another skeptical question that arises from not bothering to do the most elementary sort of research, such as reading the literature provided by the credible vendors. To take the case of ULTra, the front and back panels can be opened in an emergency, and the guideway is walkable (and has a guard rail). If you don’t check your facts, your attempts to argue against PRT, far from carrying weight, will merely discredit you.

“(eg fallen tree branch wedged into the track). Big cranes to lift out the cars?”

You are indulging in special pleading. If a tree fell across a road or a railway line, service would be severely disrupted until cranes were deployed. Ditto, if it falls across a PRT guideway. You’re arguing as if somehow you think that your argument applies against PRT, but magically doesn’t apply to other modes.

@Max Wyss

“… yeah, 6 meters above ground with a 25 cm high guard rail…”

Yet another false assertion that is contrary to the obvious and easily checked facts. The PRT guideway has a guard rail that is about 4 or 5 ft high, as documents explain and numerous pictures show.

@Charlie Dube:

“The more successful transit is, the more unbearable it becomes. It only takes one crazy or inconsiderate person on the vehicle to make everyone miserable.”

Totally agree. People use public transport when they are forced by circumstance. When the level of congestion on the roads and in parking gets unbearable, public transport ridership rises until the road is bearable, and then it stops rising — the lack of comfort and speed, as well as the inconvenience, crowding and the risk of uninvited encounters with nutters all being matters taken into consideration. Hence, the majority of cities in the developed world are unable to boast that most commuter trips are made on public transport, let alone most trips.

@Aron Levy:

“Or are you just assuming that every promise of PRT is true and every promise of mass transit is false?”

It does rather seem to be the case that most of the promises made by mass transit are false. When projects are announced, the promised cost of implementation is usually half or less the final cost. Promised ridership and farebox recovery, by contrast, are usually much higher than is realized in the end. If PRT is merely no worse than mass transit at delivering on its promises, it will be a better system than mass transit.

@Michael D:

“Again, costs are completely ignored. If your density cannot support even reasonable bus service, then how the hell can you justify building a PRT network?”

If you look at ULTra’s website, you will find details of sponsored and independent studies that compare their PRT against buses, and their PRT comes out better on both costs and services. It might not apply in all situations, but it looks as if PRT can out-compete buses in a wide range of applications.

“privacy has its downsides. If we’re talking urban transit, those pods will get nasty. Smoking, litter, etc.”

London buses – no privacy, but when I have ridden them, I have observed filthy interiors and appallingly inconsiderate passenger behaviour. So, if it’s a choice between a filthy private vehicle and a filthy crowded one, I guess the filthy private one might just win by a nose. It’s like being miserable and rich – better than being miserable and poor.

You are listing exceptions. Only a tiny fraction of rail services around the world are privately owned and operated, and even most of those are dependent on infrastructure that was built at taxpayer expense. Others that are ostensibly privately run in fact receive substantial state operating subsidy, on top of the state funding of infrastructure.

@Michael Setty wrote: “On the topic, “We’re from Missouri: Show Me.” Why don’t YOU seem to understand THIS POINT?”

Actually, you HAVE been shown, but refuse to see it. The Cabinentaxi test track ran 2 dozen vehicles continuously, nonstop, for over a year. This was in 1978, and the vehicles ran at 2.5s headway during this entire trial, HALF of what you claim is the minimum.

Now, you may shut your eyes and ears to facts like this, but it doesn’t change reality.

Further, you seem to imply that aircraft-level reliability can’t be achieved on the ground. Why not? An airliner is orders of magnitude more complex than an ULTra pod, so why wouldn’t it be possible to design a pod to be as reliable as an airliner?

And yes, of course, maintenance and inspections ARE part of the plan. Part of the inspection process will be automated, as the vehicles have built-in health monitoring. As for regular human inspection, which is also part of the plan, how difficult do you think it will be to inspect a pod? Do you think a pod inspection will be anywhere near as difficult or time consuming as airliner inspection? Once again Michael, you seem to be vastly overestimating the complexity of these vehicles. They are barely more complex than a golf cart, and in ULTra’s case, they use mostly proven, off-the-shelf components. I would guess that a vehicle inspection would take no more than a few hours, likely much less than that.

I have to say, this seems to be random nitpicking on your part, not unlike your earlier concerns about the use of aluminum. You seem so dead-set against the mere idea of PRT that you’re now attacking even non-controversial items. Maintenance of transport systems is as old as transport itself, yet for PRT it suddenly becomes a deal-breaker. Highly reliable systems have been engineered for decades, yet for PRT it’s impossible. Aluminum wheels have been in use for years in the automotive industry, yet for PRT you predict it will fail.

From my perspective, it’s all just scare tactics meant to discredit a new technology.

My view is very widespread. The overwhelming majority of people in developed countries use public transport rarely or not at all, and indeed spend thousands of pounds to avoid doing so (i.e., buying, insuring, parking, fuelling and maintaining a car). Even in Japan, where the trains are famously efficient and punctual, the majority of journeys are not by public transport.

PRT doesn’t even try to handle rural journeys, which is where cars predominate. For urban journeys, transit can and does have majority modal share – for example, rail alone has 60% of the commute modal share in Greater Tokyo. In Singapore, where car ownership is at Manhattan levels, and Hong Kong, where it’s half as high, the rail + bus modal shares are even higher.

Of course, it helps that none of the above cities engages in US-style road socialism. But if $1 million/lane-mile roads need subsidies, what hope does a $7-15 million/track-mile PRT system have? To run profitably, US roads need to double the user fees or more; PRT would need to cost at least 14-30 times more than US roads do right now.

Only a tiny fraction of rail services around the world are privately owned and operated

Except in Japan, which has 40% of the world’s rail ridership, and in most of the rest of developed East Asia…

And the alternative to public transportation, highways, is never privately operated. Local public transportation is private or profitable in many cities; local streets never are, even in countries where mainline freeways are profitable through tolls.

When projects are announced, the promised cost of implementation is usually half or less the final cost. Promised ridership and farebox recovery, by contrast, are usually much higher than is realized in the end.

Promised ridership was higher than realized in the 1980s, when there was no empirical experience in the US – i.e. the same situation as PRT. From the late 1980s onward, US light rail ridership projections were usually correct. For every underperformer like San Jose, there’s a Phoenix, with ridership substantially higher than projected.

If you look at ULTra’s website, you will find details of sponsored and independent studies.

Yes, and I’m sure none of them has a conflict of interest and all were published in top quality journals and are highly regarded by the experts… I’m sure they’re nothing like the sponsored and independent studies touted by the Tobacco Institute.

“Automated cars which can operate on streets are a LONG way off. From a technical standpoint, operating vehicles in a mixed-mode environment is *orders-of-magnitude* more complex than operating on an exclusive guideway. And even if automated cars were here today (far from it), they do not solve the congestion problem on our already-overburdened streets.”

Mike C, I’m not sure why you’d make a claim. If by long way off you meaa more than 5 years, sure. But if you mean more than 10, I wouldn’t be so confident. VW is about to send a car up and down Pikes Peak without a driver. We have cruise controls in passenger vehicles today that respond to other cars. The technology is nearly there. The time aspect is likely dependent on social acceptance, not the technology.

Automated cars don’t solve the congestion problem? Why would you say that? They’ll greatly increase the capacity of the roads, most of with are not overburdened except by a small amount for a few hours a day.

There is a mountain of difference between riding up Pikes Peak and riding in city streets, pun intended. None of the existing driver assist technologies operates without human oversight, and I don’t see that changing for at least a decade, probably more.

The problem is, when dealing with uncontrolled settings, it is exceedingly difficult to design systems that can handle unpredictable situations nearly as well as a human can. Sure, you can get part of the way there, i.e. alarms that signal a driver when drifting out of a lane or when a collision is pending, but that final step of eliminating the driver entirely is a huge challenge.

My guess is that we will start to see very low speed automated vehicles, i.e. 20mph or less, and mainly in controlled settings. The automated parallel-park is the first implementation of that. But higher speeds and mixing with traffic is a long way off.

The basic problem, in my view, is that automated control algorithms will not be able to mimic the inherent judgement that a human has, not for decades, and therefore automated vehicles will have to operate in a paranoid mode, stopping for obstacles that humans would easily dismiss as inconsequential.

But that’s just my impression, I could be wrong. I have worked on artificial intelligence algorithms in software for more than 10 years (in my case, language algorithms) and I’ve seen firsthand the enormous challenges that must be overcome to build software algorithms which can interpret data as well as the human brain. I’ve seen how easy it is to go from 0% to 60% accuracy in such algorithms, and then how much more difficult it gets after that. I personally think the challenge is exponential — the effort needed to go from 50% to 55% is probably 1/10th that required to go from 55% to 60%, which is 1/10th the effort to go from 60% to 65%, and so on.

So I think we’re decades away from fully automated vehicles on city streets. But as I said, I could be wrong.

Alon:Surely there’s an institute selling automated cars that will be happy to provide studies for you proving that automated cars are completely safe.

There’s no “think tank” selling automated cars I know of, but there is this site touting “robo-cars” as being just around the corner: http://www.templetons.com/brad/robocars/. Arguing with the fellow behind this site is even more pointless than with PRT advocates.

@Alon, what do you think of the cabintaxi trials, where they ran 24 vehicles for over a year nonstop without a fault and were approved to carry passengers?

How about the ULTra test track, which has been in operation for several years and was used to garner UK regulatory approval? Or the Vectus test track, which has had a similar record? Or the Raytheon test track from the 1990s? Or the 1970’s era fully functional scale model which demonstrated the Aerospace Corporation’s work? Or the Japanese CVS test track from the early 1970s?

Or, how about the Morgantown PRT-like system, an automated system operating for almost 40 years, carrying 16,000 passengers per day, and not a single serious injury or death?

Next time, do some research before embarrassing yourself with your ignorance. Implying that PRT’s safety case was somehow “bought” like some back room tobacco deal is patently absurd.

It’s also very interesting how Mike C understands that the complexity and effort to obtain more competent AI goes up exponentially, as he succinctly outlines, but fails to see that the complexity, potential areas where the system can fail, and the overall potential for system failures ALSO go up exponentially as still unproven PRT networks increase in size, the number of vehicles, and the number of stations.

In a very simple PRT system like Heathrow, there are only two possible origin-destination pairs, “Carpark A” and Carpark B” to/from the terminal station. If this very elementary network operated in a non-airport context, there are only three origin-destination pairs.

But if you go to the next step, such as my theoretical 25 station PRT network for in Winona, MN has a total of over 300 station origin-destination pairs, plus dozens of complex connections between various routes and loops, as well as 200 or more PRT vehicles required, if my traffic estimates are reasonable at 15,000-18,000 trips per day, vs., 1,500 or fewer daily at Heathrow.

Keep in mind that the Heathrow system has been delayed another year, due to various kinds of teething problems–and it is a very simple system compared to the sorts of networks that PRT advocates want developed next.

At Heathrow, the human clientele will certainly be very well-behaved, consisting mostly of well-heeled business air travelers who are unlikely to leave graffiti or otherwise abuse the equipment.

But in a general public PRT network, system operations will be subject to the wild card of the “human factor” including my favorite, the “Little Old Lady in the PRT Station” problem, as well as unruly teenagers, gang members who excel at leaving their marks in unsupervised vehicles (Mike C, have you ever seen the back of an urban transit bus in a large city??), the occasional pervert and drunk, as well as the various other things that currently bedevil public transit, e.g., THE PASSENGERS!

There are many non-technological factors that can upset the automated PRT applecart, which is one of the reasons why it will often be quite impractical to run a PRT system “at the edge” of its maximum throughput without some significant margin of error.

This is a central reason why I’m highly skeptical of PRT. Yes, minimum 2.5 second headways at times may be possible on some systems, such as demonstrated with Cabintaxi 30 years ago, but not reliably at close to the limit for hours on end, when the technological complexities and ongoing maintenance challenges of a highly complex technological system are considered, let alone the confounding myriad of human factors, such as the non-tech saavy little old ladies who “hog” a ticketing/dispatching interface for 4-5 minutes before boarding their pod, assuming they can easily find the correct pod particularly during busy times.

I find it amusing that you consider PRT technology as anywhere in the same league of complexity as robocar technology.

PRT vehicle trajectory control is absolutely trivial. Modern computers can do such calculations billions of times per second, to any degree of precision required. And routing is almost as simple. That GPS on your dashboard calculates near-optimal routes that cover thousands of miles over tens of thousands of interconnected roads, and does it in seconds. Take a wrong path, and it recalculates automatically, in seconds, and that’s in an embedded processor that’s probably 1 fiftieth the computing power of a PRT control room computer.

And you are comparing it to robocar technology, which must process megabytes of image, terrain, and radar data every second in an attempt to identify and classify arbitrary obstacles in real time! Do you have any idea how complicated these artificial intelligence algorithms are, Michael? Last week I installed the latest version of Google Picasa image software, which has face detection, and it took several days to identify faces in about 10,000 photos. Even then, detection failed about 15% of the time, and identification failed probably 40%. Robocars have to do this kind of work in realtime and without error!

And you’re comparing this complexity to the trivial routing, trajectory, and scheduling algorithms of PRT? Really, Michael, this is almost as bad as comparing PRT complexity to the space shuttle.

To underline the simplicity of PRT control, recall that two 1970s era systems (Morgantown and Cabintaxi) demonstrated conclusively that PRT algorithms were safe and robust. These systems were running on room sized computers that had a tiny fraction of the computing power of that singing Elvis greeting card you got for your birthday! Think about that: PRT systems were controlled by a level of technology that we now purchase for $5 in a drug store and throw away.

And you want to compare it to cutting edge robocar AI. Absurd.

Cabintaxi and Morgantown were doing it 40 years ago, when room-sized compu

What “factors”? Larger networks? The algorithms scale linearly; if you have 10000 vehicles instead of 10, it’s simply 10000 CPU cycles instead of 10. But even that linear increase doesn’t matter, because modern computers can already handle PRT algorithms for millions of vehicles without difficulty.

The old granny? She takes longer to board and other passengers just go to another waiting vehicle. Gee, that was difficult. See, the problem is that you’re used to the little old lady boarding a bus, where she would delay the other passengers. Station throughput would be marginally affected, but line throughput would not be affected at all.

Graffiti and Vandalism? Transit authorities have been dealing with these problems for years. The difference with PRT is that passengers actually rent individual vehicles, so vandals can be more easily identified, at least in theory. This should be an effective deterrent, along with CC monitoring; but if not, then it’s no worse than rail transit has had to deal with. And it has nothing to do with throughput.

Breakdowns? We’ve already dealt with that: aircraft-level reliability, self-monitoring systems and preventative maintenance should make service interrupting breakdowns very rare (remember the analogy to planes falling from the sky?), and even when they do occur, there are contingencies as with ANY transit system that fails

What else Michael? You’ve given us little old ladies and vandals and vague predictions of “unpredictable human factors”… and clearly they will not be any more problem for PRT than for other transit systems, and often less of a problem for PRT.

So do you have anything else? I sincerely hope not, because with every post here you show us more of what you don’t know, and honestly I’m starting to feel sorry for you.

“PRT doesn’t even try to handle rural journeys, which is where cars predominate.”

So? The majority of trips are taken in towns and cities. Even if PRT never winds up offering rural services,

“rail alone has 60% of the commute modal share in Greater Tokyo.”

Yes, there are a small number of cities in the world where the majority of commuter trips are done by rail, but there is no sovereign country in the developed world where the majority of trips are done by rail. According to Japan’s official statistics, 29% of domestic passenger travel was by rail, and 65% by road – 6% being by bus (2007 data).

“Except in Japan, which has 40% of the world’s rail ridership, and in most of the rest of developed East Asia…”

Japan indeed has the highest rail ridership in the developed world, and has a high proportion of private involvement in the industry, but is nonetheless not a real exception to the situation I described. Although a large proportion of the Japanese rail system is privately owned and operated, it depends heavily on infrastructure that was built by the Japanese state at (vast) taxpayer expense. Furthermore, the Japan Railway companies could not exist as viable entities today without the fact that the Japanese government bailed the industry out to the tune of tens of billions of dollars in the 1980s prior to privatization. Japan’s ridership is helped by the restrictive road traffic policies the country has, which includes widespread use of toll roads (such that highways not only pay for themselves, but also subsidize other roads). Yet, the majority of trips in Japan are not by rail. “Most of the rest of developed east Asia” is South Korea, where the railways are mainly state-run (Korail). Rail’s rideshare is high (25%), but not as high as Japan’s. Wikipedia tells me that despite being a city-state, and being the global leader in road charging, Singapore has a smaller proportion of people commuting by rail than Tokyo – barely more than 50%. Hong Kong would nicely fit the picture you wish to paint, but it is a city in China.

“Yes, and I’m sure none of them has a conflict of interest and all were published in top quality journals and are highly regarded by the experts… I’m sure they’re nothing like the sponsored and independent studies touted by the Tobacco Institute.”

Let me clarify: there are sponsored studied, and there are independent studies. The independent studies I am alluding to are not sponsored by ATS or the PRT industry, but by the EU, and by European governments through the usual channels of such funding. There is no more reason to suppose that these studies are tainted by conflict of interest than there is in the case of studies funded in the same way that say favourable things about rail or bus transit. These independent studies report that PRT has the potential to beat buses and light rail in a wide range of situations.

[[“PRT doesn’t even try to handle rural journeys, which is where cars predominate.”

So? The majority of trips are taken in towns and cities. Even if PRT never winds up offering rural services, ]]

I meant to say, the majority of trips are taken in towns and cities. Even if PRT never winds up offering rural services, this will make little difference to PRT’s ability to compete with buses and trains, which, incidentally, are incapable of providing good rural services economically.

Bruce: Singapore has a large bus system; most of those non-rail trips are not done with private cars, which most Singaporeans do not own. South Korea has mixed private and public ownership of the subway networks; most lines are not operated by Korail.

Somehow you keep dodging the fact that urban travel in East Asia is mostly done by public transportation. So no, the whole “Public transportation is so bad we must build a low-capacity system for the same cost as transit” argument isn’t sound. Sorry.

And it’s nice you claim there exist independent studies, but you keep linking to ULTra’s website for them.

Mike: Morgantown runs PRT at longer headways than you claim are possible for PRT. Morgantown headways are 4 seconds, whereas the capacity figure you give for PRT requires headways of less than a second. Train control system costs rise very quickly when you try to shorten headways; in Europe they’re spending many billions on a train control system that will finally allow mainline trains to run 30 tph, up from 24 tph in the old system. Said system would of course not be able to quadruple train frequency over existing systems the way you think ULTra can quadruple frequency over Morgantown.

The Daventry PRT study, a vendor-neutral study conducted by transit consultants SKM and hosted on a local city government site. I believe the study was government sponsored.

Fundamentals of Personal Rapid Transit – a book published in the 1970s documenting the research done by the Aerospace Corporation, a US government contractor which studied PRT for several years on government funding. Because their work was government funded, Aerospace Corporation owned non of the intellectual property associated with that effort.

Furthermore, Masdar City is deploying PRT on the recommendation of their independent consultants. PRT was selected as the technology before any individual PRT vendor was selected.

The notion that PRT technology and feasibility is tainted by financial influence is silly

Re: Morgantown: no, actually Morgantown runs at 15 seconds headway. Cabintaxi, however, ran at 2.5s and ran fleet endurance testing for over a year, uninterrupted. Do you realize the significance of that? Michael Setty has expressed concerns about PRT endurance for a 3 hour rush period, ignoring the fact that Cabintaxi ran vehicles for thousands of hours nonstop, without fault.

So Morgantown disproves the notion that an automated small vehicle network cannot be safe in a real world replete with Setty’s “grannies and vandals”. Cabintaxi’s trials disprove the notion that a system cannot run at 2.5s headway safely and reliably over a long period of time. Regulatory approval of modern systems provides further validation of the short-headway PRT case.

What more do you need? Independent studies? See above. Real-world validation of modern designs? That’s coming this year (Heathrow and Masdar).

What else do you need to finally stop saying PRT is unsafe/unreliable/incapable of low-headway operation?

It is clear that PRT is (is going to be) a disruptive technology. It seems likely to me that, at the least, it will have a significant role to play in places like airports. 2getthere operated a successful prototype of its Park Shuttle PRT-like system at Schipol Airport for many years and this system is now running successfully at Rivium in Rotterdam. ULTra’s Heathrow PRT system gives every indication of success – I have ridden both of these systems (Heathrow & Rivium) and am privy to much of what has gone into their development. These are serious companies developing serious systems. Think again if you think these people have not already considered and addressed the issues raised here.

It is still uncertain where PRT will go beyond niche applications like airports. I believe it will ultimately play a significant role in urban transportation but I also believe it will first play an important supportive role. Much of the discussion here is about PRT versus all other modes. We should be thinking more along the lines of how PRT could support and facilitate existing modes. I think PRT and rail modes could work well together with PRT feeding the rail, allowing for less rail stations and thus higher speeds.

One thing is certain, the transportation systems we have today are not working well (read my blog Transportation is Broken at http://www.prtconsulting.com). If PRT could solve some of our present problems, it behooves us to seriously consider it. The fact that PRT has taken so long to emerge has more to do with institutional inertia and fear of disruptive technologies, as expressed here by many, than the technology itself. Every new technology from the light bulb to the airplane or the telephone has been claimed to be unworkable or unnecessary.

“Somehow you keep dodging the fact that urban travel in East Asia is mostly done by public transportation.”

I’m not “dodging the fact”, you are. I stated a fact, namely that most travel in developed world countries (including even Japan) is not done by public transport. I even cited Japanese official statistics, which give approx, 60% to the car, just under 6% to the bus, and just under 29% to the train. You can’t deny these facts, so you try to give an impression of denying them by bringing in a different topic, namely, the proportion of commuter trips in a few very dense cities. Yes, the majority of commuter trips in those cities is by public transport, forced by road congestion and the high cost of parking, but that does not contradict the statement I made. As I said, most people all over the developed world, will, if they can afford it, spend thousands of dollars a year to avoid having to travel by mass transit. You have not refuted that claim.

You did the same thing with the proportion of rail passenger transport that is privately run without subsidy. I said that around the world, most rail passenger transport is publicly subsidized or publicly owned and run, and that even in those places where it is ostensibly privately owned and run, it is in fact usually dependent on publicly subsidized infrastructure, and often dependent on publicly subsidized operating costs. This is irrefutable, so instead of trying to refute it, you change the subject again in a way that could sound like a refutation to a casual hearer. In South Korea, most rail services, as I said, are state run. This is not contradicted by your statement that most metro lines in Korea are not operated by Korail. In fact, your statement doesn’t even contradict the claim that I am going to make now, which is that most metro rail services in Seoul are wholly or partly publicly owned and operated. To be precise, Korail runs 310 km of Seoul’s metro lines, and shares the running of 125 more km with Seoul Metro, while only 268.6 km are fully operated by private sector companies. The simple truth is, there are very few places in the world where rail transport can beat the car in the open market and make a profit. One of the key criteria is very high population density.

The other statement you make that sounds like a contradiction of what I said turns not to be, either. It seems to be based on a misunderstanding. You said, “Singapore has a large bus system; most of those non-rail trips are not done with private cars, which most Singaporeans do not own.” The official figures are here:

On trips to work, 25% are by public bus only, 7% are by private chartered bus or van, 9% are by MRT only, and 14% are by a combination of MRT and public bus. That adds up to 55%. So, you see, I was already counting the buses when I said that “barely more than 50%” commute by public transport.

In Singapore, the total mode share for private vehicles, taxis, and cars + MRT is 32%, according to your link. The balance of the 32% + 55% is made by “others” and “no transport required” (walking, working from home).

“Okay, 2.5 seconds… still very low-capacity, 1,500 per direction per hour. Are you going to take back your statement that PRT can be run safely at a capacity of 5,000 vehicles per direction per hour?”

First, 2.5 seconds is good enough for a wide range of applications. Second, when organized as a network, a PRT system does not need as much capacity per line as rail does in order to achieve the same passenger throughput. Third, there is no reason to suppose that 2.5 seconds is the limit of what is possible. Cabintaxi was successfully operated on the test track with 0.5 second headways, to see what was possible, but since they weren’t expecting to deploy the system with such short headways, this testing was not extensive.

As a bit of a newcomer to this debate, I’m a bit puzzled at one thing.

There seems to be some agreement above that mass transit and a successful urban deployment of PRT (should one come to fruition) might serve different niches–traditional mass transit thrives in high-density areas, whereas is better suited towards enabling car-free living in reduced density areas.

Yet many of the comments from PRT supporters above–continue to frame PRT as a replacement for mass transit (or at minimum, as more worthy than traditional mass transit for the limited funding that’s available); and some continue to promote the myth that rail transit is only suitable for cities like New York or Hong Kong, with five or six figure density figures (persons/square mile).

Why is this?

Wouldn’t there be more interest in advocating PRT to developers?

I think that many transit advocates would be less hostile to PRT if PRT advocates weren’t trying to steal their lunch money, don’t you think–especially given that the technology seems best suited for a different role than the bus or the train? Instead, much of PRT advocacy seems to be geared towards diverting the pittance of transportation dollars that goes to rail–rather than getting a chunk of the much larger sum that is allocated towards roadbuilding.

Speaking of money, it also seems to be the case that most of the PRT advocates here have a financial interest in the success of PRT–quite a few of you are working for PRT vendors, it appears. I can’t think of anyone who posts here who works for Siemens or Bombadier or Gillig–the pro rail and pro-bus folks here are mostly transit users and advocates who care about the quality of the service provided, NOT about winning orders for their employer or their stock portfolio.

I never said 5000 vehicles per direction per hour for a single line. The only time I mentioned 5000veh/hr is in the concert venue example, where the venue would be at the intersection of several PRT lines.

What I claimed regarding single line capacity was that 3000 vehicles per line is technically achievable target, corresponding to 1s headways. No current system is approved at one second, but at least two are designed for safety at one second. What remains is to demonstrate that capability to regulators and prove that the desired safety levels are achieved. That work is ongoing.

So why are they currently limited to 2.5 and above? As Michael Setty will tell you, current regulations are limited to the “brick wall stop” rule, which necessitates that all follower vehicles on a track-guided system must be able to stop fully at a reasonable deceleration in the event of a “brick wall stop” in the leader. At PRT line speeds, the brick-wall stop requirement limits headways to 2.5s.

But the brick wall stop rule is essentially tailored to the constraints of human operated trains. When that rule were conceived, there was no small-vehicle, automated, track-guided vehicle system in existence. Trains were under human control had stopping distances measured in miles, and the brick wall stop constraint was required to keep those systems safe.

PRT is a completely different system, and can be made safe without the brick wall stop rule. Some aspects of PRT that allow for sub-brickwall stopping distances while still maintaining safety:

(1) It is fully automated, meaning that reaction times are measured in milliseconds rather than seconds.

(2) PRT systems also feature seated passengers which means the emergency deceleration rate can be larger than that for a system with standing passengers.

(3) PRT systems operate on exclusive guideways, without at-grade intersections, and with stations located on sidings. Therefore, the possibility of stopped vehicles on the guideways will be exceedingly rare. But, rare as it would be, even a stopped vehicle would not be a problem, because the breakdown would not cause an immediate stop but a gradual slowdown to stop, and thus followers would have time to slow down themselves and/or automatically reroute around the breakdown. It would have to be a sudden, brick wall stoppage, which, barring an act of God would be all but impossible on an exclusive guideway There’s no way a fully loaded tractor-trailer could block a PRT guideway, as it can block an at-grade railroad crossing.

Again, it comes down to aircraft-level reliability in the vehicles, which coupled with exclusive guideway all but eliminates the scenarios where a brick-wall stop would occur.

(4) If an act of God does cause a brick wall stop, i.e. a tree falls across the guideway (exceedingly rare, but possible), PRT at 1s headway would still be less catastrophic than a bus or train would under the same tragic circumstances, for the simple reason that PRT carries fewer passengers per vehicle. If a tree falls on a moving train, the entire train of hundreds of passengers suffers fatal decelerations; if it happens to PRT vehicles running at 1s headways, a few vehicles and no more than half a dozen people suffer a fatal result.

So there is a compelling case to be made that PRT operating at 1s is, at the very least, as safe as all other existing transit systems, and likely more safe than at-grade modes which must deal with unpredictable auto/truck traffic.

So, the question arises, why isn’t ULTra operating at 1s? The answer is simple: regulations have not yet been changed to reflect the PRT model. Earlier PRT efforts (e.g. Taxi2000) tried to force the issue by pushing for deployment at sub-second headways, and that approach failed miserably: it was too much risk. So ULTra is taking a less aggressive approach: start of at ~3s, which regulators can approve without touching the brick-wall standard, and as operational experience is gained, start the process of regulatory approval at shorter headways. They will do this the standard way, by proving to regulators that such headways are well within the acceptable safety standard, but they will be starting with the experience of an existing system at 2.5s, as opposed to starting from nothing but designs on a page.

So my point all along is that 2.5s (~1400 vehicles per hour) is a current limitation, but it is not necessarily a permanent limitation, and now with multiple systems actually being deployed, the brick wall constraint may fall sooner than many people think.

OK, that’s the long winded technical discussion on headways. Now for the more user-friendly discussion:

The next time you are driving in your car on city streets at around 25mph (~40kph), estimate the distance between you and the vehicle in front of you. If it’s less than about 1.5 car lengths, you are driving at 1 second headway. If it’s less than 4 car lengths, it’s 2 seconds headway. (assuming a car length of 16 feet).

Another test: next time you are on a deserted street (make sure nobody is behind you! :-)), coast to around 25mph, and then apply the brakes to stop within 1.5 car lengths. That’s a 1 second headway brick wall stop. I’ve done this myself, and even without a seatbelt, it is not at all dangerous for seated passengers. Now, if such stops were a normal occurrence in a transit system, it would be unacceptable; but having to stop that fast only in infinitessimally rare, act-of-God type events, it’s not a problems.

So, in a nutshell, 2.5s is established technically and accepted by regulators; 1s is established technically but not yet accepted by regulators. There is certainly a risk that regulators will never approve 1 second headways, but I believe that risk is small enough to proceed. And even if regulators never accept it, I still believe PRT plays a useful role in many situations, even at 2.5s.

In any case, if the trials at Heathrow and Masdar go as expected, this entire conversation may be moot in a year or two, as regulators might approve lower headways with operational experience.

In Singapore, the total mode share for private vehicles, taxis, and cars + MRT is 32%, according to your link. The balance of the 32% + 55% is made by “others” and “no transport required” (walking, working from home).”

Again, you’re the one who is dodging. You have not contradicted any of my statements by your statements regarding transport in Singapore. Most importantly, you have failed entirely to contradict my general statements about global preference for not travelling by mass transit when possible, and the commercial non-viability of rail in most places. Regarding the Singapore statistics specifically, if we exclude the “no transport required” category, then the % travelling either by rail or by rail+bus rises from 55% to 57%. If we further assume that all the journeys classified as “other” combination trips involved a part that was covered by rail, then rail accounts for all or part of 31% of commuter trips in Singapore. This means that your earlier statement (below) was incorrect:

“for example, rail alone has 60% of the commute modal share in Greater Tokyo. In Singapore, where car ownership is at Manhattan levels, and Hong Kong, where it’s half as high, the rail + bus modal shares are even higher.”

The rail+bus share is lower than the figure you claimed for Greater Tokyo.

• Costs
As it presents itself, the costs are rather high, for what a system provides. At the moment, these systems have a novelty factor, and get some development bonus. When it comes down to hard numbers, in comparision with other options for a particular application… we will have to see.

• Scalability
When it gets beyond a simple ring or another simple layout, the complexity of the system increases dramatically (keeping in mind that the system is highly distributed intelligence). It may be possible to overcome the problems, but the question remains, at what price.

• Acceptability
Outside of an enclosed application (such as aeroports, amusement parks etc.), the impact of the system’s infrastructure must not be neglected, as it has to be above or below ground level. How well that is accepted in residential areas has to be shown.

• Percieved safety and security
The system is automatic and has small units. This prevents any kind of social control. Outside of enclosed applications, well, maybe even within, people will act … like people… as it happens in public elevators as well. Also, the vehicles run on a rather elevated flimsy roadway, and are rather sealed. This will raise questions

• Maturity
This is more a question on how PRT systems are marketed. At the moment, but that might be with all kind of “unconventional” transit systems, there are lots and lots of buzzwords, but not much substance. Apparently, the publications are aimed at politicians (understandable… they are the ones who decide about budgets). Also, there are claims which are hardly (or very expensive) to prove. This and also the technical reliabiltiy has to be shown.

Mike, there’s no point in implementing a system for urban use before it’s appropriate. So yes, put more test tracks, but until capacity becomes high enough to justify $14-30 million per mile, i.e. barely lower than the cost of LRT, it shouldn’t be used for urban travel. Remember that both PRT and LRT have transfer stations and multiple lines and have higher capacity at the transfers; PRT’s ability to have more lines is limited.

The brick wall rule is not absolute. In the next generation of ERTMS, trains will be able to account for the fact that the next train is moving forward, which will allow them to run closer together than the brick wall rule says. For high-speed rail, it will increase maximum frequency from 13 trains per hour in current-generation systems to 19. This has nothing to do with whether the train has a human operator or not; all trains used for urban transit today are subject to positive train control, which stops them if the train operator tries to exceed the speed limit or run a stop signal. Such a control system will have benefits for both PRT and rail, increasing the capacity of both. But even then, one-second headways are unlikely – for trains the increase in capacity is 33-50%, not the 150% required to take 2.5-second trains to 1-second trains.

Bruce, your general statement is incorrect about a decent chunk of the developed world. If you exclude areas with gigantic road subsidies, e.g. the entire US and rural areas anywhere else, then your statement’s wrong about most of the developed world.

“Yet many of the comments from PRT supporters above–continue to frame PRT as a replacement for mass transit (or at minimum, as more worthy than traditional mass transit for the limited funding that’s available); and some continue to promote the myth that rail transit is only suitable for cities like New York or Hong Kong, with five or six figure density figures (persons/square mile).”

Some mass transit is operating where it is not really viable, and is only able to operate with very high subsidy and/or low frequency of service, due to the ridership demand being insufficient to fill the vehicles. In those cases, I would be in favour of PRT replacing mass transit. There are also lots of places where PRT can operate that are currently not served at all by mass transit. These are PRT’s “low hanging fruit”, so I don’t think there is any serious threat in the short term to mass transit jobs from PRT. If vendors of mass transit systems are worried about a threat from PRT to the long-term future of their business, they can always develop their own versions of PRT. There is nothing preventing them. After all, the key patents for PRT guideways, switches, etc., have all been in the public domain for years. I have no affiliation to any PRT vendor.

“Bruce, your general statement is incorrect about a decent chunk of the developed world. If you exclude areas with gigantic road subsidies, e.g. the entire US and rural areas anywhere else, then your statement’s wrong about most of the developed world.”

First of all, to talk of “gigantic road subsidies” is special pleading. Almost all railway infrastructure exists by virtue of gigantic stat subsidies.

Second, your assertion is backed up by no statistics. We have seen that even in the country with the most comprehensive, all-round-best and most heavily used passenger railway network in the world (Japan), 60% of trips are by car. I am not going to hold my breath waiting for the official statistic you will produce to show that in the EU15 countries, rail ridership is higher than car ridership, because you and I both know that no such statistic exists.

I’ll agree that “some mass transit” operates where it requires a larger subsidy to provide acceptable level of service (what level of “subsidy” makes a service “viable”, and what LoS is “acceptable” are political decisions, so I’ll punt on these), but there are often good reasons for doing so. Many transit services are run for social benefit, rather than for mass-mobility or environmental reasons; generally these things aren’t light rail.

But that’s a strawman argument: Except for toll roads, streets have a farebox recovery of zero–and even if you count 100% fuel tax revenues as part of the revenue equation for streets, they still require subsidy. Many try and hold transit to a higher standard of financial performance than they do streets.

That said, there are STILL many arguments out there that PRT systems ought to be deployed instead of light rail systems for applications where ridership and/or service quality is expected to be low for a given budget. Perhaps, but again–there are other transit technologies that are neither LRT nor PRT that also fill this niche well.

Let me ask a question: Why, do PRT supporters suppose, production PRT systems have not been implemented other than a handful of cases?

Is it:

* Opposition and FUD from bus and rail interests (manufacturers, transit unions, and others who have a financial stake in other forms of transit)
* Opposition from transit opponents altogether–the auto and petrochemical industry, the political right wing, and/or motorists who like their cars and don’t want to pay for anything else that they don’t plan to use?
* Intransigence and/or excessive risk-aversion among transit planners, politicians, and others responsible for the design and operation of specific systems, who are reluctant to try something new?
* Issues with regulatory authorities?
* Objection from “urbanistas”, some of whom oppose suburbia and low-density development altogether (including for reasons other than environmental concerns), and who may be opposed to any transport mode which caters to the suburbs?
* Objection from NIMBYs, who might dislike PRT infrastructure in their backyard (even those more than willing to tolerate streets)?
* Objection from private developers and their financiers, who prefer to build (or finance) development in forms which are well-known and well-accepted, and unwilling to risk money on something new?

I’ll agree that “some mass transit” operates where it requires a larger subsidy to provide acceptable level of service. . . Many transit services are run for social benefit

In many cases, it may turn out that greater benefit can be obtained at lower cost by PRT than by bus or rail.

Except for toll roads, streets have a farebox recovery of zero–and even if you count 100% fuel tax revenues as part of the revenue equation for streets, they still require subsidy.

You are doing that special pleading thing again. Rail is much more heavily dependent on subsidy than roads. How much of the road system is paid for by the drivers varies from country to country, but in the UK where I am, around 60-80% of a driver’s fuel bill (depending on current prices of fuel) is a duty paid to the state. Add to that annual Vehicle Excise Duty, which can be up to £400 a year for a car, Value Added Tax on cars at 17.5%, and compulsory insurance policies, also taxed, and it turns out that drivers and car owners, rather than the state (as routinely but inaccurately claimed by rail advocates), pay for the road system.

Many try and hold transit to a higher standard of financial performance than they do streets.

And many, evidently, do not.

Let me ask a question: Why, do PRT supporters suppose, production PRT systems have not been implemented other than a handful of cases?

I don’t think there’s any big problem on that score. It costs millions and takes years to get a test track developed, so we should expect that stage of development to be fairly slow. The first successful PRT test track (Cabintaxi) was built 30 years ago. In the end, mere luck (in the form of an inconveniently-timed financial crisis hitting the German government) prevented its deployment. The second one (Raytheon) was a flop, many obvious errors having been made. The third one (ULTra) was built in 2002 and was a success, leading to the first commercial sale. That’s not too bad, compared to other innovatory technologies that involve high initial development and start-up costs. Some ideas with apparent promise never get that far. Others are tested for years without ever getting to a sale.

Why is mode share even relevant anyways? If you are trying to measure effectiveness, I would think mode share divided by overall investment would be a better metric; given the trillions of dollars that have been ground up, loaded into cement mixers, and poured onto the ground, I’m sure mass transit doesn’t look so bad.

But ignoring that–the whole “transit only gets X% modeshare” lines of argument misses the boat completely. One form of the argument simply exhorts that transit’s share of transportation dollars ought to be capped, until transit can somehow pull itself up by its bootstraps and boost its “share” ex nihilo, which may in fact happen if and when gas hits $5/gallon in the US. A more pernicious form of the argument is that transit is therefore a “failure” and should be defunded.

Were either argument applied to PRT–the mode share of which is so tiny, that it would be more easily expressed on a logarithmic scale–there wouldn’t be any argument about PRT. Of course, that argument isn’t made about PRT, as its a new technology–but that brings me back to my point about share-over-investment above.

However, there does seem to be a related argument floating about–that low-density transport forms dominate, therefore we should fund more of them. I have no objection to that–if the funding is diverted from auto infrastructure. But Bruce seems to be suggesting that mass transit, due to its lower “share”, is somehow failing cutting the mustard, and that the solution to this is to either build less of it and more of low-density infrastructure; or replace current transit modes with Something Else–and in either case, PRT is offered as a solution.

Just because 60% of trips (according to Bruce) in Japan are taken by autos, or zillions of people in Manhattan get around in taxis, doesn’t mean that the rail lines in either place are failing. If there is an application for PRT (in Japan) its in reducing that 60% number, not in reducing the 40% or so currently served by mass transit.

I would think mode share divided by overall investment would be a better metric

If we take investment into account, rail looks even worse. Rail was the dominant mode of transport until the mid 20th century. Since then, it has sucked in countless billions in subsidy, while delivering an ever-diminishing mode share. Meanwhile, car drivers pay for the roads through various taxes and duties. In the UK, car drivers pay approximately £40 billion a year in fuel duty, vehicle excise duty, etc., but the government only spends £10 billion on the roads. In other words, car drivers not only pay for the roads in full, but they also subsidize the railways, despite that the railways only provide 1/15th as much service (measured in passenger-km) as cars.

until transit can somehow pull itself up by its bootstraps and boost its “share” ex nihilo, which may in fact happen if and when gas hits $5/gallon in the US.

Unlikely. The preference for driving over train travel is impressively resistant to price. Petrol is $8 a gallon in the UK (due mainly to fuel duty), and yet the mode share for cars is 87.8%.

A more pernicious form of the argument is that transit is therefore a “failure” and should be defunded.

I think it’s a good argument. Let all systems duke it out on the market. My bet is that if they do, trains will soon be extinct, but buses will probably survive in a few niches, and PRT will thrive.

if the funding is diverted from auto infrastructure.

You repeatedly suggest that the auto infrastructure survives on subsidy. It does not. Indeed, as we have seen, in countries (such as the UK) where the auto infrastructure, far from being subsidized, is treated by the government as a cash cow, the car remains the overwhelmingly dominant mode of transport.

Just because 60% of trips (according to Bruce) in Japan are taken by autos

As for cars, you’re only counting direct spending on roads, not spending on pollution reduction, carbon offsets, and all the other environmental externalities of roads. The fuel taxes offset the externalities, partially; Greg Mankiw has argued that driving generates $2.21 in pollution externalities per gallon, and another $1.00 in carbon externalities. No country sets its fuel taxes significantly higher than the total, which doesn’t even include military protection of oil sources…

The idea that all fuel taxes should go to direct road spending only is a uniquely American idea, peddled mostly by motorist clubs and rural populists going back to the 1910s. Britain instead went for taxes discouraging pollution. So in Britain, roads at least pay direct costs, if not indirect ones. In the US, they don’t; the state of Texas has done an audit and found that not a single road in Texas pays more than half its construction cost, and some pay 16%.

I’m not discussing share vs “subsidy”, by which I assume you mean “funding not paid for directly by users”, I’m talking overall. Trillions of dollars have been spent on road construction over the years; and build-out of infrastructure and the like, and as you note, many communities have been designed around road infrastructure, with acres and acres of real estate consumed by parking lots, driveways, and neighborhood streets. Your argument seems to be, essentially, that “this is what we have, therefore we shouldn’t bother trying to fix it”.

Among the externalities of roads not listed by Alon include increased expenses to provide utilities to development, increased expenses to provide density-sensitive government services such as education (which requires in many places a specialized form of public transit–the school bus–because general transit is impractical), fire service, mail delivery, law enforcement, etc. Low density makes everything more expensive, and this cost is often born by the general public, just not motorists. (A common rhetorical device used by anti-transit advocates is to assume that since most people own cars, such distributed costs aren’t a subsidy, because motorists pay them anyway).

But again, I’ll ask: Why the broad based attack on transit, and the suggestion that PRT is a replacement for transit, not for the car? If you were to say to me “we should spend less money outfitting suburban communities with streets, and instead consider small-scale PRT systems”, I’d be all ears. However, when I hear that “transit sucks, as proven by the fact that nobody rides it”, you sound just like the Wendell Cox’s of the world. Virtually every criticism of transit you’ve given is chapter and verse Randall O’Toole, and we’ve heard it all before. And it makes many of us wonder–use of, well, “gadgetbahn” as a wedge to block or delay transit funding is a longstanding tactic of the build-more-roads crowd, and when you walk and quack like that particular species of duck, don’t be surprised when transit advocates regard your motives with suspicion.

I’m not against PRT per se (although I’d like to see more small successful projects before I’d be in favor of more large-scale deployments), I am against the notion that it should replace transit however.

If you want transit advocates to be your side, instead of not, it would help your cause greatly if you didn’t keep trying to pee in the transit advocates’ pool. There’s probably more money for PRT in suburban development, and such would make the job of transit agencies much easier, if they weren’t having to send mostly empty busses into the suburbs every hour to provide lifeline service. But I don’t see remarks from you as to how a suburb designed with PRT infrastructure would be an improvement over a car-based suburb–whether for the developer’s pocketbook, the resident’s pocketbook, in terms of quality of life, or in terms of environmental factors. Instead, all I see in this thread is specious reasons Why Transit Sucks.

I am a transit user. I have lived in and used transit as my primary means of transport in Pittsburgh, PA, Wash DC, Atlanta, GA, Seattle, WA, and San Dego, CA. I am a PRT advocate because I want better transit.

Buses are the predominent form of public transit in the US. Unless a bus system is so small as to not be able to justify its own fuel depot, bus systems do not generally pay fuel taxes. In other words, they have free use of the majority of their infrastructure. Even with free infrastructure these systems can not recover O&M – not mention capital costs – from the fare box. The reason for this is twofold. Drivers are expensive and running buses empty is expensive.

PRT suffers from neither of these issues. Unfortunately, PRT infrastructure is not free. While nowhere near as expensive as LRT infrastructure, PRT infrastructure is not cheap.

I am constantly amazed and amused by opponents arguements against short headways. In the US, we accept as SOP headways of less than 2 seconds on every freeway in the country. Headways performed by irrascible, incompetent, highly variable humans on a “guideway” with unrestricted lateral movement. Yet having the same operation performed by fault tolerant computer on a resticted grade separated guideway – where the worst that can happen is to rear end the vehicle in front of you – is deemed to be impossible.

I am irritated by transit “advocates” who do not use transit themselves. If it’s good enough for me, it damn well better be good enough for you! I still remember my first transit meeting in Seattle. I got up and asked how many people arrived at the meeting by transit. 3 people – including myself – raised their hands. Who the hell were the rest of these people to be telling me what my transit should be?

Michael Setty is a “transit consultant” who makes his living pushing buses and LRT. He has been invited repeatedly to join the Transit Innovators (TI) listserve on Googlegroups (easily accessed via http://www.ATRA.org). On this listserve we have people who are engineers, economists, computer programers, and system vendors. At least two of these system vendors are former aerospace engineers. We are still waiting for Mr Setty to show up.

What part of “changing the subject” do you fail to understand? Your arguments are fallacious, because they depend on changing the subject. Your claims regarding commuter trips in a handful of particularly densely populated cities in Asia have no bearing on my general claims about the popularity and economic viability of mass transit. They are simply irrelevant, and bringing them up as if they were relevant is a fallacy.

As for cars, you’re only counting direct spending on roads, not spending on pollution reduction, carbon offsets, and all the other environmental externalities of roads. The fuel taxes offset the externalities, partially; Greg Mankiw has argued that driving generates $2.21 in pollution externalities per gallon, and another $1.00 in carbon externalities. No country sets its fuel taxes significantly higher than the total, which doesn’t even include military protection of oil sources…

This time, your comment is relevant, but your claim is false.

Supposing, for the sake of argument, that Greg Mankiw’s estimates of the externalities of petroleum are not tainted by bias and exaggeration, your claim that no country sets its fuel taxes significantly higher than that sum is false. The tax on a litre of petrol at the pump in the UK is currently £0.5419 fuel duty, plus VAT at 17.5%. The typical pump price of a litre is £1.09. Convert that into US gallons and US dollars, and the tax is $4.78. Significantly higher than $3.21. The taxes in Germany, Netherlands and Norway are nearly as high.

UK drivers pay FOUR TIMES the cost of the road system in taxes on car ownership and driving. And I haven’t even included municipal parking charges. You can factor in all the externalities you like (even medical bills and workdays lost caused by accidents). On any reasonable calculation, UK drivers pay all of them. Yet, nearly 90% of trips in the UK are made by car. The notion that car driving subsists on subsidy is a myth. The case of the UK is an existence proof that if you took all subsidies out of the road system, people would still drive.

@EngineerScotty:

Trillions of dollars have been spent on road construction over the years; and build-out of infrastructure and the like, and as you note, many communities have been designed around road infrastructure, with acres and acres of real estate consumed by parking lots, driveways, and neighborhood streets.

By the same token, trillions of dollars have been spent over the years on track, viaducts, tunnels, stations, rolling stock, and various other railway infrastructure. Also, many communities have been designed around rail infrastructure. Indeed, it could be reasonably be said that most or all major cities in Europe are designed to a large extent around their 19th century rail infrastructure. It’s probably true of some US cities, also. The ring of suburbs that surrounds many large cities is also a product of that rail infrastructure. Train termini and depots, not to mention the lines themselves, consume acres and acres of real estate. Yet, trains only serve a small fraction of journeys. It’s scary to contemplate what the landscape would look like were all journeys taken by train.

We should not forget, meanwhile, that even if we eliminated private cars, we’d still need roads for goods delivery, emergency vehicles, buses, and bicycles. While most of the parking spaces would no longer be required, and some roads could be made narrower, a lot of the infrastructure we see that is associated with cars would still be there. The Romans found it useful to build wide paved roads, and they had no motor cars, nor even dreams of motor cars.

Your argument seems to be, essentially, that “this is what we have, therefore we shouldn’t bother trying to fix it”.

I am arguing no such thing. I think a revolutionary shift is much to be desired, but not a shift towards mass transit. That would be a backward step. Pushing to get people onto trains is a misdirection of effort. If pollution, CO2 emissions and fossil fuel consumption are your concern, getting people to drive more fuel-efficient cars could be achieved at low cost through legislation, and would make more of a difference than spending vast sums to extend railway passenger services.

But again, I’ll ask: Why the broad based attack on transit, and the suggestion that PRT is a replacement for transit, not for the car?

Again, you are attributing things to me that I have not said. If various ridership studies are correct, PRT will obtain far higher mode share than buses or light rail when used as an urban circulator. Obviously, this entails taking mode share from cars. My support for PRT therefore entails support for replacing car trips with public transport.

The reason I’d like to see PRT replace trains and buses though is this: travel by train and bus is generally pretty unpleasant (though there are exceptions, such as the Shinkansen I mentioned earlier). PRT would be a more pleasant way to get around. Therefore, if it works, I would certainly welcome it, and would be eager for it to replace trains and buses as much has possible as soon as possible.

However, when I hear that “transit sucks, as proven by the fact that nobody rides it”, you sound just like the Wendell Cox’s of the world. Virtually every criticism of transit you’ve given is chapter and verse Randall O’Toole, and we’ve heard it all before. And it makes many of us wonder–use of, well, “gadgetbahn” as a wedge to block or delay transit funding is a longstanding tactic of the build-more-roads crowd, and when you walk and quack like that particular species of duck, don’t be surprised when transit advocates regard your motives with suspicion.

You are adding to your previous fallacies the ad hominem fallacy of “guilt by association”. Just because some of my arguments remind you somewhat of arguments made by other people whose views you disagree with does not mean that my views are the same as theirs. I don’t know if anyone at all holds the views you ascribe to the people you name above, but I certainly do not see PRT as a “wedge to block or delay transit funding”. I see it as a form of transit that I would like to see in operation, and like to use – unlike trains and buses, which I generally dislike using. I would love to live in a town that had an extensive PRT network, so I never had to drive on routine trips. I could ride my mountain bike to a nearby PRT station, take the PRT to the edge of town, and then go for a ride in the country. Sounds great to me, and actually more convenient than the car, in that particular scenario, which buses and trains never seem to be.

If you want transit advocates to be your side, instead of not, it would help your cause greatly if you didn’t keep trying to pee in the transit advocates’ pool.

I do not care one jot about how “transit advocates” (whoever they may be) feel about PRT. If they are intelligent, they will see PRT’s benefits, and advocate it themselves as the best form of transit for many applications. If they are not smart enough to see the promise of PRT, I see no reason to respect their views.

Instead, all I see in this thread is specious reasons Why Transit Sucks.

One does not need specious reasons as to why transit sucks (or mass transit, at any rate). Anyone who has used transit at least a few times can think of a few very real and cogent reasons why mass transit sucks.

VAT is a general tax, not just a fuel tax. All goods and services are subject to it.

Not all goods and services, actually. Many things are exempt. Educational services, sport, some cultural services, books, children’s clothes, food and drink, disability aids, medical prescriptions, insulation, and mass transit are among the large number of things exempt or zero rated.

pstransit:On this listserve [Google Transport-Innovators group) we have people who are engineers, economists, computer programers, and system vendors. At least two of these system vendors are former aerospace engineers. We are still waiting for Mr Setty to show up.

But you have no one who has ever actually worked “hands on” in public transit, particularly at the operations level as I have for 30 years, as far as I can tell. You certainly would have mentioned such individuals–if you had any on the T-I list.

I am not going to join the “Transport Innovators” Google group because it is a waste of time arguing with PRT true believers, who have the gumption to lecture me about what I actually or should know about transit operations “on the ground.”

I don’t presume to lecture aerospace engineers about the numerous details and “tricks of the trade” in their profession, nor do I lecture software programmers about the intricate details and various hacks and tricks required to be successful at what they do for a living.

But I’ve been the subject of name-calling, accused of getting paid by the “light rail industrial complex” and not knowing anything about public transit planning or operations, despite having written dozens of transit plans over my career, as well as dealing with numerous transit operating, finance, management and institutional issues over the years. As well as lectured by a software programmer who clearly understands the complexity of AI, but shows little acceptance of the myriad complexities, particularly human, of operating transit, PRT or otherwise, in the real world.

Reasonable people will understand if I don’t bother with such an errant waste of time.

BTW, I have more than two papers or presentations by PRT advocates that, interpreted correctly, shows that Vuchic’s point about the capacity and economics of PRT are absolutely correct. I’ll post something on this to my website very soon, after I get some real work done–so it may be a few days.

• Costs
Booz Allen Hamilton found PRT to have lower capital and operating costs than other transit except BRT
• Scalability
An excellent point. A number of vendors claim their control systems scale but this has yet to be proven.
• Acceptability
We have developed a methodology for determining how concerns about issues such as visual impact weigh in against advantages such as reliable non-stop travel with little waiting. See http://www.prtconsulting.com How to Get Into PRT/Community Outreach. We have only applied this once with results showing visual impact was not a concern to the community (an army post). Admittedly this is a unique community. The point is that every community should decide questions like this for itself, not have that decision made for them by transit authorities and the people commenting here.
• Percieved safety and security
ULTra has run passenger trails and found very little resistance to automated vehicles. Here in Denver one must ride the automated people mover to get to concourses B and C at DIA. No one complains. If you were met in the lobby by an elevator with an operator would that not RAISE your concerns? We have grown entirely accustomed to automated elevators. That said, this is still an issue that must be addressed.
• Maturity
The fundamental technology has been proven to be reliable by the Morgantown PRT system which has completed over 140 million injury free passenger miles at transit level of service A (conventional transit would have injured over a hundred). This is a group rapid transit system that is actually more complicated than PRT. It is rickety and Heath-Robinson by modern standards but has operating costs around $1.50 per passenger. In fact Morgantown has answered many of the questions raised here. Yes, it was a disaster when built, but it was experimental and it was exploited for political reasons. There is a huge amount to be learned from Morgantown but we seem to insist on arguing all these points in theory rather than researching what the NY Times called a “White Elephant turned into a Transit Workhorse”.

What we are lacking is vendors with years of proven reliable in-service experience with their specific technology. This situation seems to be rapidly changing but will obviously take years. 2getthere is amassing considerable in-service testing with its PRT-like Rivium system. They have had one non-injury accident (due to human error). ULTra has undertaken considerable successful reliability/endurance testing – but none in-service yet.

There is indeed much to learn from Morgantown. The most important lesson is the need for much larger vehicles than 4-person podcars, if an automated guideway system is to operate effectively and efficiently with sufficient capacity. This includes line capacity andproviding sufficient station throughput to meet peak demands, at least in markets where there is enough potential transit traffic density to justify construction of expensive fixed guideways in the first place. Again, Morgantown is a case study proving many of the points made by Vuchic a long time ago.

To Peter Muller: Thanks for the comments, which are a positive change in tone to some other messages in this thread.

Actually there was one thing I forgot to enter in my reasoning earlier: Fares and Fare Collection. So far, it seems that the existing systems are essentially “free” (in the sense of no direct charge per trip, but either at no cost, or paid for by the owner or the community etc.). Please correct me if there are systems which have a “singe ticket” concept.

About automated operation: Automated operation is pretty common, as said. People movers are almost in all major airports, and subways are getting more and more automatic (even mixed operation (manned and unmanned trains mingling on the same tracks) has been proven to be very successful in Nürnberg, for example). One thing is, however, with all these systems, and that’s the simplicity of the configuration; most operations are linear, some circular, some Y or star-shaped. But that’s about the most complex we can get. … which gets us to the “scalabiltiy” point, where we seem to agree that it is an open question.

To Peter Muller and Michael D. Setty: So, if one of the conclusions from Morgantown is that bigger vehicles are needed, what would the difference be between “bigger PRT vehicles” and, for example, VAL vehicles?

I think the size of bigger vehicles would depend on the likely traffic volumes that a corridor is projected to produce. While Morgantown runs with 8-seat, 12-standing vehicles running at 15-second headways (240 cars per hour at maximum, with up to 4,800 passengers capacity per hour, in principle), either an LRT or more conventional automated guideway with significantly larger vehicles in the VAL range or larger, would have been simpler, and probably somewhat cheaper to run, allowing West Virginia University to operate service during low demand times when school isn’t in session, like on Sundays.

The Morgantown system works for what it is. Rebuilding it with the same technology probably would be cheaper than tearing out the existing system, if only because of the massive sunk investment in the system’s massive infrastructure. In fact, I think this is the plan that university and city decision-makers are pursuing with the Federal government.

Getting back to the original story about the pods at Heathrow, I think this is a good idea serving primarily as a “local circulator” while also acting as a “commercial test track”

In this application, PRT really sould NOT be considered as a replacement for the existing line-haul mass transit to Heathrow itself. The Tube and the HX train (and possibly AirTrack in the future) would still give much higher capacity direct to the trerminal itself. But if costs and reliability prove reasonable, I can’t see any reason why the initial parking lot function could not be extended through loops and/or branches to also pick up the nearby hotels, rental car lots and offices along the North Perimeter of Heathrow and then into the T1/2/3 complex. The flow of hotel patrons, staff, etc. onto PRT coming from the terminals and associated rail stations would be within the line capacity of the PRT system; use of PRT as the circulator gives better schedule flexibility and operating costs for the time disbursed travel of these potential users.

In the scenario I propose above, there is no need to transport *ALL* patrons coming off a line-haul metro network into pods as suggested much earlier in the comment thread. If you pictured a more urban setting, again you would still have the largest destinations directly at terminals on the line-haul routes, and the transfer to PRT would only serve the fraction that is going further than a comfortable walk away. “Unecessary” tranfers to PRT for a short distance from the line haul station could be discouraged through PRT station placement (larger gap from line haul, closer spacing further out?) and through pricing.

AL:
I agree that the Heathrow PRT will certainly have more than enough capacity initially than likely demand from the carpark it will serve. It remains to be seen if there are enough cars, though, depending on peak demands of the business travelers served.

If the Heathrow PRT system is expanded, I think they’ll find that larger vehicles similar to Morgantown would be more helpful, and provide fewer bottlenecks at stations during the still occurring peak periods. This however, would require heavier guideways at a higher cost than claimed by ATS. Certainly low volume “PRT” operation is possible at Heathrow, as Morgantown demonstrates.

As I’ve emphasized all along, there always needs to be some room for operating error and service disruptions, in Morgantown’s case provided by larger vehicles, scheduled service during peak times, a scheduled “circulator” during the day, and longer than “on the edge” headways, e.g., every 15 seconds vs. every 3 second, or what exactly the Morgantown PRT technology is capable of in theory.

Actually Michael Setty, I disagree quite strongly that a lesson to be learned from Morgantown is that larger vehicles are necessary or even desirable. One of the problems at Morgantown was the very high capital cost caused, in part, by the large infrastructure needed for the large vehicles. Instead of 20 passenger vehicles every 15 seconds, 4 passenger vehicles every 3 seconds provide the same capacity, require much lighter infrastructure (lighter than a footbridge) and provide a seated ride for all with much less waiting. Now do you get the beauty of the PRT concept? By the way, both ULTra and Vectus have safety approvals down to three second headways.

A further problem with large vehicles is the difficulty filling them and still providing direct non-stop service when there are more than a few stations.

Historic problems with PRT systems such as Morgantown and Rosemont have been related to people thinking along conventional transit lines and wanting to change the network of numerous small vehicles into a corridor of fewer larger vehicles. Rosemont failed because of vehicle size and other issues. Morgantown succeeded despite both of these problems. However, it is now very difficult to expand because of them.

The deadweight weight of the vehicle is not proportional to the number of people in it.

Tiny 4-person pods are carrying an absurd amount of deadweight, though better than cars.

Larger vehicles carry much less deadweight.

While weight per axle is *one* issue in guideway construction — and a major one, certainly — another one is simply the number of vehicles crossing it. Run a “light” 4-person vehicles over your “footbridge”-weight bridge every 2 seconds and how often will you have to replace it? Every year?

You pay VAT if you drive to work, but not if you take the bus or train.

So?

So mass transit is subsidized — not just directly, but also through the tax system — while car driving is not. (If anything, car driving is penalized by the tax system.) This bears upon two claims I have made, and which you have pretended can be refuted, but have not refuted, because they are irrefutable.

The first is that mass transit services, and passenger railways especially, rarely pay for themselves, and would not, if left to the market, be able to pay for themselves in most places in the developed world where they operate. (The history of bankruptcy and bad debt in the industry highlights that fact.) Yet, by contrast, the private car as a mode of transport continues to thrive when not subsidized. The UK is an example of a country where the private car thrives and even dominates despite taxes and subsidies being tilted massively in favour of mass transit.

The second is that people don’t generally like mass transit much, but rather see it as something to be endured when necessary, and avoided when possible. In the UK, despite the advantage of subsidy given to mass transit, car driving is far more popular, illustrating the simple truth is that mass transit is not loved by most people, and people are willing to spend thousands of pounds a year to get a more pleasant, quicker, more convenient alternative.

These simple truths are what I stated and defended over the course of most of our discourse, and you have – mainly by the tactic of changing the subject – been avoiding acknowledging them, while not managing to refute them.

In this application, PRT really sould NOT be considered as a replacement for the existing line-haul mass transit to Heathrow itself.

Too late: it has already been considered for precisely that purpose. If PRT can operate at 1 second headways, which it should be able to do at least on simple loops, it can match the capacity demand of many line-haul applications.

@Alon Setty:

Peter, are the vehicles promoted by ULTra 4-person? I was under the impression PRT vehicles were for 2 or at most 3 people.

I’m surprised you haven’t read up on the ULTra system to the extent of knowing that it employs four-seater vehicles, given that you have seen fit to pronounce very confidently on its potential and limitations. That PRT should ideally use 2 or at most 3 is an opinion that was expressed by J E Anderson, but clearly not a view with which ULTra (or for that matter Vectus or 2Getthere) concur, since they all employ vehicles with four seats each.

So mass transit is subsidized — not just directly, but also through the tax system — while car driving is not.

No… mass transit isn’t subsidized, any more than groceries are. In some areas, like New York, groceries are tax-free, while prepared food at delis isn’t. Not even the fast food industry shills claim that they’re subsidizing supermarkets on that account. The luxury goods industry doesn’t whine that it’s subsidizing cheap clothes, and people who sell gifts don’t complain that they’re subsidizing education.

What’s so damn special about cars that they have to enjoy the lowest possible tax rate on everything and that everything they pay has to go to roads? What next – saying that income taxes on car-oriented subdivisions is an assault on the car? (You know, sometimes they do tax relief for poor inner cities… clearly, it’s a subsidy for walking).

You do realize that apart from passing references to PRT, you’re basically shilling for highways, right?

Mr. Mueller, please wait for my future post at http://www.publictransit.us, using references from PRT advocates, showing how the PRT concept will not work beyond very light volumes, due to the problems of fare collection, dispatching and wait time at stations–an area where scheduled services can match and beat PRT, contrary to the still unsubstantiated claims of PRT advocates.

Yet, by contrast, the private car as a mode of transport continues to thrive when not subsidized. The UK is an example of a country where the private car thrives and even dominates despite taxes and subsidies being tilted massively in favour of mass transit.

Without delving into the figures for the UK, I must say that subsidies are not the only factor in making cars appealing. If most Britons live in suburbs designed for cars, then it’s only natural that most trips are by car and that the car is the preferred mode of travel — even if this is somewhat expensive. But that’s comparing apples to oranges. If you want to make claims about what transportation modes people prefer, you need to look at transit modal share on transit-competitive trips. How can you prefer mass transit if you don’t have it? (Note: a winding bus route to God-knows-where with hourly frequency isn’t competitive.)

Have you read Vuchic’s analysis of PRT vs rail? Are you fully prepared to defend it, or is your comment simply an appeal to authority?

Do you know, for example, that Vuchic compared PRT capacity to trains running nonstop at 70mph and at <30 seconds separation?

In that comparison, PRT capacity looked tiny, but it was hardly a true comparison. To be useful, trains have to stop at stations, which significantly limits real world capacity.

Now, technically, Vuchic’s comparison was correct, because he presented PRT in the “way capacity” chapter, which is a theoretical presentation of the absolute capacity limits of a transit guideway. That’s fine; it’s a textbook so it’s useful to compare the theoretical boundaries of a system under discussion. The problem is, Vuchic dismissed PRT as a viable mode in that theoretical discussion, without further analyzing how it would compare in a real world setting.

If Vuchic had continued his analysis in following chapters, where stations and stops were considered, he would have found that while rail capacities are significantly altered by the existence of stations, e.g. by a factor of 4 or more, PRT capacity is completely unaffected because all PRT stations are offline!

Do you see the problem here? Vuchic analyzed PRT versus other modes at their theoretical (and completely unrealistic) best. Other than a purely express train running on a line with no other traffic, no real world system could possibly hope to approach theoretical “way capacity” limits that Vuchic used in his analysis.

In reality, the PRT capacity gap for most real world applications was much less than Vuchic’s analysis made it appear. True rail capacities in cities are 1/3rd to 1/10th Vuchic’s theoretical maximum “way capacity” if they have to make station stops, and especially if they operate on city streets at rush hour.

So was his analysis technically “wrong”? No. PRT theoretical maximum way capacity is far below that of rail. But it didn’t tell the whole story. It’s kind of like comparing a Prius vs a Ferrari for city travel, and using maximum speed as the only metric for comparison even though the vehicles will never operate on streets that exceed 40mph. Of course, Ferrari’s maximum speed would dwarf the Prius’s, but that would not be grounds for dismissal of the Prius, which is as capable as the Ferrari (indeed, more capable) for the intended use.

Mike, are you fully prepared to defend statements about the cost of PRT when one includes stations? Because when you need multiple berths at major destinations, the cost increases.

And your “true rail capacities” in cities are a fraction of what’s already been achieved. We’ve been over it already. Light rail is capable of 20,000 pphpd, and modern heavy rail is capable of 50,000; both figures have been achieved in some cities and approached in many others. Even US cities sometimes come pretty close – e.g. Boston’s light rail at 13,000, and New York’s heavy rail at 31,000. The capacity figures Vuchic gives for mass transit in his books are in line with those empirical numbers.

One question for the PRT advocates: what happens when it snows? Trains for the most part keep running in light snow, and systems that are sufficiently prepared for it can keep running even in fairly severe snowstorms. PRT might have more of a problem. How would snow be cleared off guideways? How much would braking capability be affected by the snow, given the rubber tires? How would the automation deal with the snow? Keep in mind that the rubber-tired Montreal Metro is 100% underground or otherwise covered (including yards) precisely because of this.

There you go again, raising the high capacity rail strawman. Let me repeat: I have not and would not suggest that any current PRT system replace Boston, NYC, or any other heavily used rail system in a big city.

I am suggesting that PRT be applied in low-to-moderate-sized cities where there is no existing transit at all, and where the densities do not justify a heavy rail or high-end light rail investment. In such cities, PRT can introduce a transit culture to residents who are used to using their cars 100%, with a transit mode that is much more like their car than any other form of transit, and which does not suffer the inefficiencies of a poorly utilized light rail system.

I fail to see how NYC or Boston would have any relevance to such a proposal.

As for Vuchic’s numbers, tell me, what rail line in the world runs at 320,000 passengers/hour? That’s the maximum number on Vuchic’s way capacity graph which he uses to dismiss PRT, which you’ve indicated is “in line” with empirical numbers.

As for PRT stations, ULTra’s cost numbers include stations and vehicles, for a reasonable application. More station density than that which ULTra assumes would, of course, cost more.

I am an external observer of the ULTra system, so don’t quote me, but I would guess that an elevated 3-berth station would cost in the $200-500k range, including a small elevator. So an extra 10 stations per mile would be an extra $2-5M per mile.

Adding berths to existing stations would be much less than that, probably on the order of $30-50k per berth.

Note, most PRT stations would be very small, on the order of 1500-2500 sq ft, and would feature very few amenities, closer in form to a bus stop than a rail transit station. This makes them cheap and lightweight.

Furthermore, PRT opens up the possibility of integrating stations into private locations, such as hotels. In those cases, the public cost per station could be significantly less.

I stand by my statements that PRT can be implemented for a cost per unit capacity that is on par with rail in many cities. Now, if you’re talking about Calgary, which started planning in the 1960s by setting aside ROW for future rail lines, then rail may be more competitive. But, in North America, Calgary is the exception and most cities are not positioned whatsoever for rail. It is these cities where PRT would be competitive with, and quite possibly cheaper than, a streetcar or light rail system that provided similar capacity.

And let’s not forget, would provide a much higher level of service in those applications. There is a huge difference between 7-minute frequency with transfers versus fully on-demand service with no transfers, especially for car-loving passengers in a typical medium-sized US city. So even IF PRT costs a little more than rail, it provides a LOT more in terms of service.

Apologies for addressing Alon Levy as “Alon Setty” in two posts above.

Meanwhile:

@Michael D:

Without delving into the figures for the UK, I must say that subsidies are not the only factor in making cars appealing.

Huh? I think I have shown pretty conclusively that subsidies are not making the car appealing in the UK. Quite simply, car driving in the UK is not subsidized, whereas mass transit is.

If most Britons live in suburbs designed for cars, then it’s only natural that most trips are by car and that the car is the preferred mode of travel — even if this is somewhat expensive.

Most Britons do not live in suburbs designed for cars. Most Britons live in cities, towns and villages that existed a thousand years ago (and are documented in the Domesday Book of 1086), long before the car. Obviously, they’ve grown since then, but a lot of the growth was before popular car ownership, and street layouts reflect the fact. Examination of a street map of Britain will quickly reveal that the the typical UK town is not designed around the assumption that everyone will get around by car. This is also true of most of the suburbs that exist on the fringes of Britain’s cities, which were built when the norm was that the middle classes commuted by train, and thus they invariably have a street network that converges upon a Victorian railway station, and exhibits an obvious inadequacy of parking space on (or off) most residential streets. Those commuter railways are still in heavy use – it’s just that their role is supplemented by motorways.

20th century “New Towns”, such as Milton Keynes and Crawley, which really are designed with car users in mind are very much the exception rather than the rule in the UK.

As if that weren’t enough, a certain Professor Smeed at the University of London came up with the idea sixty years ago that expanding the road system to accommodate cars would be a bad idea, since it would merely lead in the long run to increased car use, and the expansion of car use would cancel out any relief to congestion that the new roads or new lanes were intended to provide. Governments in the UK ever since have been influenced by this idea, and have as a matter of policy strangulated the road system. Many towns in Britain have pedestrianized all or part of their central area, banishing the car outright, and London was one of the first cities in the world to introduce congestion charging.

Car use in the UK is advantaged neither by subsidy, nor by an urban design, nor any other official policy that favours the car over mass transit.

But that’s comparing apples to oranges. If you want to make claims about what transportation modes people prefer, you need to look at transit modal share on transit-competitive trips. How can you prefer mass transit if you don’t have it?

Every town in Britain, and every suburb of every town, has mass transit. Only rural areas miss out. People are not choosing the car because mass is unavailable. They’re choosing the car because mass transit is slow, uncomfortable, and inconvenient.

That’s a joke, right? Buses are uncompetitive precisely because they are slow and winding and they make you wait (plus they tend to offer noisy and uncomfortable ride). It’s simply not possible for either buses or trains to provide the flexibility and quickness of service or the completeness of coverage that cars provide. For every destination that a bus or train can take one to “directly” (not from A to B, of course, but from the nearest stop to A to the nearest stop to B) and without a long wait, there are countless other destinations that people want to visit that the bus or train serves poorly or not at all, but which can be reached by car or other individual transport.

There is no way to fix this using mass transit. It is the mass aspect of mass transit that militates against its flexibility, speed and convenience.

Another PRT design, the Korean Vectus system, has done extensive snow and ice testing on its test track in Sweden.

Note that PRT’s fully automated mode of operation makes it possible to continuously clear snow before it accumulates. Snow clearing vehicles could be running continuously in a storm with virtually no cost impact (because there is no driver). The only cost of this continuous snow removal is the energy cost of running a vehicle.

Without hours of accumulation typical of roads or at-grade transit, lightweight vehicles could easily keep the guideway clear. Perhaps no special vehicle would be needed at all – if every PRT vehicle has a simple deplyable show brush under the chassis, snow could be cleared by regular vehicles already in passenger service.

Mass transit is certainly subsidized in the UK. Even if you ignore the VAT break that all mass transit enjoys and the fuel duty break that buses enjoy, there are direct subsidies from the government to bus and rail services worth billions of pounds. Why are you denying easily-checked facts?

Cars are not necessarily luxury goods. Many people could not get to work or do their jobs without a car. Also, this idea that mass transit is subsidized because it is what the poor use is dubious. Quite poor people can and do own cars.

What’s so damn special about cars that they have to enjoy the lowest possible tax rate on everything and that everything they pay has to go to roads?

Huh? Where did I say cars should “enjoy the lowest possible tax rate on everything”? Cars in the UK pay a much higher tax than most things (when fuel duty is taken into account), yet I have not demanded that the tax should be reduced, even though cars are essential, and so could arguably be due the same support that buses and trains get. All I have said is that despite the financial penalties of driving, driving is more popular than mass transit.

What next – saying that income taxes on car-oriented subdivisions is an assault on the car? (You know, sometimes they do tax relief for poor inner cities… clearly, it’s a subsidy for walking).

What are you talking about now? Evidently, you are changing the subject again. There are no local income taxes in the UK.

You do realize that apart from passing references to PRT, you’re basically shilling for highways, right?

“Shill”, eh? What a laugh!

One does not have to be a “shill” for highways to admit that for most people the car generally offers a more convenient, quicker, more flexible and more comfortable way of getting around than buses or trains do.

In fact, to deny this obvious fact is perverse, and your unwillingness to acknowledge it betrays your bias.

Now, if you’re talking about Calgary, which started planning in the 1960s by setting aside ROW for future rail lines, then rail may be more competitive. But, in North America, Calgary is the exception and most cities are not positioned whatsoever for rail.

Calgary’s ROW reservation did two things. First, it limited construction cost. That would be true for every mode of transportation, whether rail, BRT, or PRT. And second, it made the main routes known in advance, so the city could upzone them and redesign buses to feed light rail; again, without such plans PRT would not succeed, either, because uniform low density would be too expensive to serve by a $14-30 million/mile system.

But Calgary is not the only city where light rail demand far exceeds the capacity of PRT – at most, it’s the only such city in the North American Sunbelt. This demonstrates competence, which is sorely lacking in the rest of the North American transit planning world. The problem is that you can’t argue for PRT on the grounds that LRT is designed incompetently, because the same urban planners would be doing the system design.

As if that weren’t enough, a certain Professor Smeed at the University of London came up with the idea sixty years ago that expanding the road system to accommodate cars would be a bad idea, since it would merely lead in the long run to increased car use, and the expansion of car use would cancel out any relief to congestion that the new roads or new lanes were intended to provide. Governments in the UK ever since have been influenced by this idea, and have as a matter of policy strangulated the road system. Many towns in Britain have pedestrianized all or part of their central area, banishing the car outright, and London was one of the first cities in the world to introduce congestion charging.

This is such a load of crap I don’t even know where to begin. In the 1960s, after Smeed released his report concluding that expanding road capacity would not reduce congestion, Britain studied his report to death and did nothing. The only country that listened was Singapore, which was technocratic enough for the government to be able to implement such things without opposition. Singapore’s road pricing program was a success, but even then, the West didn’t try to learn until decades later, when Singapore became rich and globalized and Westerners started to visit. London implemented congestion pricing in 2003, 28 years after Singapore. Calling it “one of the first cities in the world to introduce congestion pricing” is true but misleading.

Most Britons do not live in rural areas, but most Britons do not live in dense cities, either (i.e. cities where it makes sense to spend $14-30 million/mile on fixed-guide transportation). The idea that they still live in medieval city boundaries is laughable. The medieval boundary of London is the City of London. The late 19th century boundary is most of Greater London, which itself is barely half the London metropolitan area. Most of the rest was built for cars: the 19th century cities in Northern England were depopulated after the war because of urban renewal schemes. Where it wasn’t built for cars, cars don’t predominate: in Greater London, transit has a 52% mode share, private vehicles 37% (see table 1.8). And while the transit share has risen in response to congestion pricing, there was an equally large increase, driven mainly by a reduction in car traffic, in the years before 2003 (see table 1.6 in the above link).

Once again you are refuting something I never said. You wrote “The problem is that you can’t argue for PRT on the grounds that LRT is designed incompetently, because the same urban planners would be doing the system design.”

When did I say LRT is designed incompetently? The cities I’m referring to don’t HAVE LRT, so how could it be incompetently designed?

I’ll repeat, again: many cities in the US are not positioned for rail, because underground would be too expensive and at-grade would disrupt roads which are already saturated with automobile traffic. To retrofit such cities for rail is expensive, because either at-grade ROW must be acquired or it must be separated (underground or above) — expensive and disruptive.

In such cities, PRT’s lightweight infrastructure would require only a tiny fraction of the equivalent LRT ROW, would not disrupt existing traffic, would generally cost no more than an at-grade LRT ($30M/mi) while providing a similar level of capacity as that LRT (since that at-grade LRT will be competing with existing auto traffic which is already congested) and provide MUCH better service for lower operating costs, service so high that it would draw perhaps five times the mode share (10-20%) that LRT typically attracts in this kind of city (2-4%).

And every time I bring this up, you raise Calgary, NYC and Boston, three cities where transit has been in place for decades, even centuries. And then you claim that transit planners in those other cities are “incompetent” and wouldn’t be able to do PRT right anyway. Your argument is full of straw men.

PRT is the worst transit “solution” and its backers are delusional, obsessive, and quite frankly, not pleasant to be around. They are the most pathetic in a sea of already pathetic people, transit advocates.

Spokker:PRT is the worst transit “solution” and its backers are delusional, obsessive, and quite frankly, not pleasant to be around. They are the most pathetic in a sea of already pathetic people, transit advocates.

I’ll agree with your characterization of may PRT advocates and some transit advocates, with this amendment: Methinks you’re referring in large part to railfans who also fancy themselves serious transit advocates. Actually, there are many kinds of basement-dwelling dweebs who are more pathetic, who dwell on things like Star Wars, gaming, and computers. The worst combination is probably basement-dwelling dweebs who obsess on computers and PRT.

I don’t know why Mike C., my most vociferous opponent on the Transport-Innovators Google group and here, keeps referring to only one aspect of Vuchic’s analysis regarding the theoretical capacity of PRT vs. rail.

There are many other issues, mostly non-technical, that severely limit PRT’s practical usefulness. For example, the fact that even if a PRT system has been approved for 3-second headways, the operating headways will still have to be longer, 5-6 seconds, to allow vehicle merging and demerging, and giving an allowance for system disruptions caused by human and other factors. Thus at the current state of affairs, the practical capacity of PRT is limited to 5-6 second headways, allowing for the factors I’ve cited again and again. The same rule applies whether minimum allowable headways are 2 seconds or 1 second.

Mike C made the salient point that PRT system capacity would actually be limited by station capacity, not line capacity per se, a correct observation. This is shown by BART, for example, where operations through the Market Street subway and Transbay Turbe are limited by how quickly passengers board and alight at the four Market Street BART stations. If all BART cars had three doors on each side rather than the current two, a few more trains could be operated through the subway and Transbay Tube because station dwell times could be significantly reduced.

Please refer to a recent paper by John Lees-Miller, John Hammersley, and Nick Davenport. Ridesharing in Personal Rapid Transit Capacity Planning. American Society of Civil Engineers (ASCE) Automated People Movers Conference, June 2009, Atlanta. (Available at rose.bris.ac.uk/dspace/bitstream/1983/1414/1/ride_share_v16.pdf). Hammersley and Davenport work for ATS, the vendor for the Heathrow PRT system.

According to Lees-Miller et al, PRT stations capacity begins to break down with as little as 100+/- “parties” per hour during peak times. According to Figure 2, PRT station delays begin to grow dramatically over the “minute or less” promised by many PRT advocates as the number of destinations increase from a handful to even small networks of 15-25 or more stations (destinations).

As you’ll recall from my Winona paper, I estimated there would be around 25 PRT stations, so even with 114 parties per hour, average delay would be around 3 minutes–to which you’d have to add the additional time of entering elevated stations, fare purchase and vehicle dispatching. Recall also my concerns about the average length of these activities, which could range from 30 seconds for saavy cellphone users to 5 minutes or more for non-tech saavy grandmothers.

Overall, at such small volumes and a modestly complex network of 25 stations, waiting times would match those of 10-minute bus service. In a non-protected PRT setting such as a small city, 114 parties translates to about 140 passengers per hour at 1.2 persons per party (occupancy), and daily station volumes of around 600-700 daily based on typical peaking factors,e.g., 15%,. This is the total of BOTH boardings and alightings. Even the worst-performing major LRT system in the U.S., Santa Clara, has only some stations with less than this patronage.

The bus service I proposed for Winona would actually have major advantages, including better coverage with 1/4 mile or less distance from most residents, the fact that more service could be added quickly if needed, and only when needed, offsetting any speed advantage of non-stop PRT service. Bus capital costs would be an order of magnitude less than PRT even with the most optimistic cost estimates for PRT construction. Buses would have much llower operating costs, mainly due to the high fixed costs of maintaining and operating a relatively elaborate PRT infrastructure for relatively low total patronage relative to the capital investment.

The Lees-Miller paper that ATS began with an estimate of 47 vehicles needed to meet projected peak demands, but was able to cut the fleet to 18, based on “ridesharing.” That is, since the Heathrow system is very simple with only one terminal station and two in the carpark, the business traveler clientele would not be resistant to sharing their pod with strangers–again, in contrast to one of the biggest talking points in favor of PRT. Certainly PRT capacity can be increased by ridesharing, but the propensity to rideshare even in a small city such as Winona would be limited by a much wider choice of destinations and the delay problem shown in Lees-Miller et al Figure 2. “Ridesharing” in larger vehicles, e.g., Quality Bus, is a much more efficient, effective and practical solution.

The only instance in Winona where PRT ridesharing would be consistent would be for the two instances where Winona State University (WSU) currently runs two shuttle bus routes at 10 and 15 minute headways, respectively, during peak periods. If 40-passenger buses were replaced by 4-passenger pods, travel times would be lengthened by the delays found in Lees-Millers et al’s simulations, and the “hassle” factor would be greater, if only due to the increased access and wait time of elevated stations and waiting for the right pod (at the residential end of the PRT station, not all riders would be going to WSU).

@Michael Setty #203. You have totally misunderstood John Lees-Miller’s paper. His paper is about ridesharing, not about station capacity. Its about people waiting to find other people bound to the same destination. This becomes difficult “breaks down” when you have more than about 15 to 25 destinations. The number of destinations has nothing to do with PRT station capacity unless you are attempting ride sharing.

Even if you are only loading/unloading one person per T-Pod and this takes a dwell time of 20 seconds (metro trains often only stop for 10 seconds), this is 3 people per minute or 180 per hour per bay. A PRT station could have 15 or more bays for a capacity of 2,700 people/T-Pods per hour so stations are not the bottlenecks you think they are. Also, PRT stations are meant to be relatively small and numerous and thus not subjected to the demand that large mass transit stations are subjected to. Morgantown (admittedly not PRT) has processed over 3,000 per hour though one station – this includes ticketing.

FWIW, one method to shorten station dwelling time is using insular tracks with platforms on both sides; one for getting off, and the other for getting on the train. Such a layout can be found at the busiest stops of the Munich S-Bahn tunnel (at Hauptbahnhof and Marienplatz). I don’t know whether BART has a similar station layout. Another (more expensive) approach would be doubling the tracks at a station.

The paper mentioned is quite interesting, and it does put the capacities in serious relationship. The capacities mentioned, based on 3, 2 or 1 second headways can only be reached on “trunk sections”, and require a very high number of vehicles.

I can not prove it (as my math is a bit rusty), but it looks to me from reading the paper, that the capacity could be somewhat increased by pre-assigning berths and queues to specific destinations, instead of letting the passengers specify the destination when they get on the vehicle.

Michael Setty continues to assert that headways would be limited to 5 seconds due to “factors” which I have shown to be completely irrelevant. It is this kind of misinformation from skeptics that has prevented PRT from being taken seriously among transit professionals.

Let me repeat, for emphasis: The assertion that PRT headway cannot be less than 5 seconds is completely wrong, and has been proven wrong by extensive analysis and testing since the1970s. Cabintaxi maintained these headways even with merging/diverging. A line of ehicles running at 2.5s can have one vehicle diverge and the followers close the gap within a few hundred feet, with no capacity loss; similarly, a merging vehicle notifies the control system of its intent, and the control system instructs area vehicles to create a gap in which that vehicle can merge. Since that gap is quickly filled, there is again no capacity hit.

If you need a demonstration of this, take a ride on your local expressway, where uncoordinated vehicles merge and diverge all the time and surrounding vehicles automatically adjust back to typical separations.

As for the unpredictable “little old lady”, stations are offline and ULTra berths are parallel, so the little old lady has no effect on guideway capacity!

I can’t believe Setty continues to belabor this point. Headways of 2.5s are proven; headways of 1s are likely. Any assertion otherwise is a flat-out denial of the facts which were established by the 1970s Cabintaxi system.

With such a 15-berth station, the capacity limit is indeed not the boarding zone (assuming that a vehicle every 20 seconds is practically feasible). The bottleneck (as well as the challenge for the control system) of such a station is the entrance to the main guideway, where you have to get the vehicles up and running at a 1.25 seconds headway. And, in order to provide access to every destination from every berth, you will need a section through which all vehicles pass. We now could use some simple physics, and guesstimate how big that accelleration zone would become…

Also, for playing around a bit more with numbers, assuming that a vehicle would be back at that 15-berth station within 6 minutes, you would at least need 270 vehicles.

Such a system is already quite a monster, IMHO. And I would not be surprised if it would break down under its own weight… one had to do some simulations.

Max Wyss:I can not prove it (as my math is a bit rusty), but it looks to me from reading the paper, that the capacity could be somewhat increased by pre-assigning berths and queues to specific destinations, instead of letting the passengers specify the destination when they get on the vehicle.

You are correct. In other words, capacity could be significantly increased by operating in a semi-scheduled mode, and even more if each berth served a scheduled stopping service with larger vehicles, as shown by Morgantown and every real transit system. Your point shows the utter futility of PRT in coping with all but very tiny passenger volumes, at levels where its capital costs cannot possibly be justified by any rational metric. Of course, this argument and thread has hardly been rational.

Mike C., an elevated PRT system with ULTra style berths will be somewhat wider than most designs with in-line berthing, so is unlikely to be constructed due to its higher cost. And the “little old lady” problem” impacts the STATION CAPACITY issue, not line capacity per se. Any transit system, PRT or otherwise, has to have some room for error. Why you don’t get this is beyond me. I will never concede this point, and you’ll never convince me otherwise.

Mueller:A PRT station could have 15 or more bays for a capacity of 2,700 people/T-Pods per hour so stations are not the [THEORETICAL] bottlenecks you think they are.

Let’s see, 15 bays with ULTra-sized vehicles would be 300+ feet long, comparable in size and cost to an elevated HRT or LRT station. The ULTra docking bays aren’t practical for elevated stations, and add a few seconds at least to each bay’s throughput.

Mueller, you are the one who has completely misunderstood Lees-Miller’s paper.

Part of their simulation included estimates about how long the waiting queue would be at PRT stations, and how this waiting could be reduced through ridesharing. The simulation also allowed for the PRT system to deliver empty pods to the theoretical station. Figure 2 refers to the average wait per “party” whether the party is 1, 2, or 3 persons. In the case of a network with 25 destinations (e.g., my Winona PRT thought experiment), the average wait with 114 “parties” per hour (114, 228, or 342 persons) is 3 minutes; with 216 “parties” per hour and a 25 destination network, average wait of 6 minutes.

Certainly more bays would reduce the wait time for PRT at a given station, as shown in the 1978 PRT book, but in the real world station size and cost has to be balanced with likely demand and the available budget.

You’d also have to have far more accurate patronage modeling than the current state-of-the-art, which has gotten better at system level projections, but still can be highly inaccurate in station-level projections. When LRT station projections are off, the system can usually cope; if you’re low by one or two bays at a proposed PRT station, you’ll have major operational problems.

Projected PRT capacities at stations always break down because (1) you’re not going to get more than about 1.2+/- persons per party in a real world urban setting; and (2) station sizes are strictly limited; 25 elevated stations in Winona with 8-15 bays each would easily cost $3-$4 million each, putting the capital costs of PRT relative to likely capacity even higher in the stratosphere.

When “climbing the steps” or “ride the elevator,” and ticketing and destination selection is included, average total waiting time is LONGER than average waits of buses or trains running every 5 to 10 minutes, at ANY PRT station with more than a handful of passengers at a time. If this weren’t the case, Lees-Miller would also not have simulated QUEUES in the Heathrow ULTra stations, which are greatly reduced by ridesharing–as was the projected number of vehicles from 47 down to 18.

So, in the real world, Vuchic’s bottom point about PRT is made, again: WHY BOTHER with PRT beyond the tiny capacity it can offer, particularly at stations?

To continue playing numbers with our 15-berth station, it would actually be possible to build it on ground, but the access to the berths would have to be from an upper level, going down something like 2 m (how, whether stairs, elevators or escalators would only affect the cost, but not the capacity). Hmmm… elevators… lifting up the vehicles and putting them down again… another interesting idea, which would allow getting on and off from the same level, but would probably seriously extend the 20 seconds turnover time.

Anyway, the actual passenger-related area of such a station would be about 10 x 45 meters on level 1, including the passenger handling space.

However, on ground level, the station would be something like 250 x 50 meters, in a parallelogram shape.

As a comparision: a light rail stop is about 10 x 45 m (serving trains up to 45 m in length (which translates to some 100 seats plus another 250 standees), 6 m width for the right of way, 2 m each side for the platform (or 4 m for an insular platform). Such a station easily serves a train per minute (exactly, one train per minute and direction).

Max WyssAs a comparision: a light rail stop is about 10 x 45 m (serving trains up to 45 m in length (which translates to some 100 seats plus another 250 standees), 6 m width for the right of way, 2 m each side for the platform (or 4 m for an insular platform). Such a station easily serves a train per minute (exactly, one train per minute and direction).

Such a station could easily handle one LRV per minute each way, but as a practical matter only if grade separated. Three minutes is really the minimum headway without major disruption of cross street traffic and to avoid bunching of trains at traffic signals, so you’re better off running three car trains…if you need the capacity–most places don’t.

Michael, if you put the at-grade sections of LRT in transit malls, and invest in a good signal priority system you can do 2-minute headways. The higher capacity of metros comes from their ability to run longer trains; LRT trains can’t be longer than a block in order to avoid disrupting street traffic.

Mike C, I’m still holding you to what you said about PRT offering similar capacity to LRT. If it’s rated at 2.5 seconds so far, then it’s limited to 1500 vehicles per hour, less than a freeway lane (and more expensive) or a city bus, to say nothing of a light rail line.

Michael Setty, almost every assertion you are making here with apparent authority is completely, utterly wrong. As it happens, I’ve been busy today and haven’t been able to respond quickly, but I am prepared to address and correct every one of your recent misconceptions on PRT operation.

Let’s start with station capacity. Let’s assume 10% LOLP (“little old lady percentage”) and that each “little old lady” causes the cycle time to be 45 seconds rather than 15 seconds. For PRT, this means that for every 9 vehicles which load in 15 seconds, the 10th takes 3 times longer. So in any given berth, 10 vehicles load in 180 seconds, for a 18 seconds average load time, rather than the 15 seconds that would be typical of a purely younger crowd.

That’s a 20% increase, the equivalent to less than a single extra berth in all stations up to 5 berths. So if the PRT is installed in a south Florida retirement community, you may have to add extra berths per station. But in college towns like Winona, the LOLP is probably more on the order of 1-3% – insignificant.

But wait: none of this affects PRT line capacity, particularly not ULTra PRT with its parallel stations: if a vehicle takes longer to load, it sits in the station and doesn’t block the line of traffic moving past, and for ULTra, doesn’t even affect other berths in the same station. In fact, in most cases, the little old lady doesn’t affect other passengers one bit, as they just go to a different berth (most stations will have 2-3 berths).

Only in the very busiest times, when there happens to be a full station and all berths have passengers waiting, will passengers be affected, and their average wait will be 20% longer, 18s for every group ahead of them instead of 15s. Even if the berths each have 20 people waiting, which would only happen during an extreme surge such as end of a sporting event, passengers would have to wait an extra minute. Oh, the humanity!

Now consider when that same 10% LOLP is applied to light rail. Again assuming 1 in every 10 passengers is slow loading, and that most stops during busy periods will have more than 10 people loading, this implies that most of the light rail stops will have to stall a whole train waiting for the little old lady. In this case, all passengers wait for our poor LOL: everyone on the current train, everyone loading, and if the trains are running at high frequency, every train behind the the current train on the line.

So, once again we see an example where the individual, parallel aspects of PRT make it less susceptible to “human factors” than buses or trains. A high percentage of “little old ladies” (10%) only adds a marginal amount of time to PRT station boarding time, and even then only in cases where all berths in a station have lines of waiting passengers. But for trains and buses, LOLs at every stop will add minutes to the total journey time, wreak havoc with schedules, and possibly even hold up following trains coming into the station.

Thank you, Michael, for pointing out yet another way in which PRT service is superior.

Mike, could you not assume how rail would react to a high LOLP, but instead look at real-world examples? When you have rail with multi-door boarding, a slow person would cause other people to board at other doors, without much of a slowdown.

Yes, other people can board through other doors, but the train must sit and wait for every last LOL to board before leaving the station. I.e., one LOL holds back an entire train/bus for the entire duration of the delayed loading time.

Michael, I happen to know John Lees-Miller and am planning on collaborating with him on a paper for TRB 2011. I attended the presentation of his paper at APM09 in Atlanta. I think you should read it again before just asserting that I misunderstood it. Start by reading the title!

I have had enough of bumping heads here. It seems clear that there are too many emotions involved. I agree that we should not let our dreams for PRT get in the way of other good transit projects. However, I am still waiting for a conventional transit project that pays for its own operating costs and some of its capital costs and, at the same time attracts a significant number of drivers from their cars. PRT promises to be able to do this while also using a third of the energy per passenger mile of conventional transit and being orders of magnitude safer. This promise is such that I believe it behooves us to give PRT every chance to prove itself.

If you are in DC next week (Jan 11 -13), I strongly recommend proponents and opponents alike attend TRB Sessions 583 Diversified Applications of Automated People Movers and Personal Rapid Transit in the Urban Environment and 618 Performance Evaluation of Automated people movers and Personal Rapid Transit Technologies. I will be there and glad to debate any of you at that time. John Lees-Miller will also be there and presenting a paper. Also the Advanced Transit Association has its Technical Meeting January 10 at 10AM in College Park. This will be a great opportunity to learn more and contribute your opinions.

You are completely misrepresenting the thrust of that paper. That paper describes a potential ridesharing alternative for small networks which would allow them to purchase fewer vehicles to service the same demand. The authors fully acknowledge that ridesharing is not a practical solution for networks with large numbers of destinations, so this is obviously intended as a solution only for very small networks, or as a temporary “bootstrapping” solution for small pilot networks which may grow later…

…like, perhaps, a pilot application for an airport that’s starting with only two destinations but which will likely expand later. Sound familiar?

The initial Heathrow pilot has only 18 vehicles, and may benefit from ride-sharing in busy times. The operative word here is PILOT. This is the first installation of a brand new implementation of a brand new transit system. Do you think maybe they didn’t want to build 100 vehicles right out of the gate, in case that the pilot revealed issues with the initial design?

My guess (and it’s purely a guess, but it makes sense) is that ATS proposed ridesharing in order to limit the number of vehicles required for the pilot, and then if minor vehicle design problems were revealed during the pilot, the problems could be fixed in rev 2 and only 18 vehicles would need to be retrofitted. This would be entirely in line with ATS’s approach from day one: walk before running, and crawl before walking.

Having fewer vehicles for the pilot would also minimize the financial risk for the pilot customer (BAA), as the cost of ~40 vehicles would be saved should the system prove to be a failure.

And ridesharing would work well for the Heathrow pilot, because it has only 3 destinations.

Did I mention that Heathrow is a pilot system?

Now let’s consider future systems. As the number of destinations expands, ridesharing becomes increasingly less effective, as the probability that random unrelated passengers will share destinations approaches zero. It is then that the number of vehicles will need to increase to cover the demand.

And at that point, vehicles can be added. Assuming the cost of a vehicle is $50,000 (somewhat high, but these are not mass produced — yet), an additional 100 vehicles will cost $5M of additional capital, and that will cover a mile of bidirectional guideway at about 2 seconds headway. So no more than $5M per mile of additional capital per mile gets enough vehicles to saturate the guideway in the current version. And no ridesharing is needed. If PRT becomes popular, over time those vehicle costs will come down as production increases, so the cost becomes even less significant.

Dear PRT apologists: Please explain why urban PRT is better than car sharing, or why it would have any more appeal or success? What problem does PRT solve that car sharing does not, and at what cost?

Car sharing uses the existing road infrastructure (which isn’t going anywhere), existing manufacturing economies of scale, and probably substantially the same amount of energy. It certainly costs an order of magnitude or two less to implement. And the kicker: you can actually buy a shopping cart’s worth of groceries at the store and bring them right to your suburban door.

Yes, other people can board through other doors, but the train must sit and wait for every last LOL to board before leaving the station. I.e., one LOL holds back an entire train/bus for the entire duration of the delayed loading time.

In principle, yes. In practice, agencies factor those delays into their schedules and manage to maintain 2-minute headways regardless.

Car sharing does seem difficult to use for one-way trips, though Autolib’ in Paris will be doing just that. However, it raises a question: can PRT be used to commute to work? Work tends to be concentrated in CBD’s — precisely the kind of area PRT cannot serve. Can PRT serve even one 10 story office building of 9 to 5 workers? 20 story? And don’t tell me that people will want to abandon driving in order to take PRT and then transfer to mass transit (which apparently they hate).

And it certainly seems to me that PRT can’t really be used to go to the kind of big box stores low-density areas have spawned.

OK, Alon, so the problem is manageable even in a setting with serial stations and common boarding. Why would it therefore be a deal-breaker for PRT, with offline stations and individual boarding?

My point was not to say that it is a problem for rail or buses – but rather, that it would be inherently less of a problem for PRT, where offline stations ensure line capacity is completely unaffected and individual station berths ensure that station capacity is only marginally affected.

This is the kind of argument I see a lot in PRT debates, where issues such as Setty’s “little old lady” delays are raised and presented as deal breakers for PRT. However, on closer inspection, it becomes clear that PRT would be no more affected by such issues than other forms of transit, and often PRT would be much less affected due to its highly parallel and individualized design.

@Michael D: yes, I envision PRT serving CBD areas in moderate density cities. It would not, in its current incarnation, serve NYC or anything near that density, except perhaps in a transit circulator role in outlying areas.

But there are enough moderate density cities out there where PRT can play a significant role in the daily commute, especially in North America.

I view carsharing as a complement to transit. It allows people to have the occasional use of a car when they need it, but relieves them of car ownership. They would still require some form of transit for many tasks, mainly the daily commute, and in many cities PRT can fill that role.

So PRT would complement carsharing just like any other public transit system. It doesn’t have to be either-or.

OK, Alon, so the problem is manageable even in a setting with serial stations and common boarding. Why would it therefore be a deal-breaker for PRT, with offline stations and individual boarding?

PRT doesn’t have level boarding. People would need to enter a PRT vehicle and be seated first, and then the vehicle would need to close its doors. The process is comparable to this of a city bus, except that a city bus only needs to close its doors once, regardless of how many passengers get on, and that a city bus can start driving before the passengers are seated. The high acceleration and deceleration rates of PRT are only achievable if all passengers are seated.

You are missing the point. In PRT, one to four passengers enter a vehicle, sit, the doors close, and the vehicle moves. For ULTra, this happens in every single PRT berth independently, and for all PRT, it happens in every station with no affect on the line.

If one PRT vehicle loads slower than the others, it has no effect on other berths in that station, and only has an effect on other passengers IF there is a queue at that particular berth, and a marginal effect at that.

For a bus, a slow loading patron holds up the entire bus, and likely holds up vehicular traffic behind the bus. Potentially dozens of passengers are delayed by a single LOL, as opposed to the occasional PRT passenger who happens to get caught in a line behind a LOL when there are no other empty berths.

Also, to correct something else you said: PRT does have level boarding, though adults would have to bend down to get into the seat. Everyone who has ever used a car is familiar with this kind of loading.

Mike, loading for a car is slower than loading for a bus, per passenger. But the issue is not what happens at one berth; it’s that you need many berths to have high capacity, and those can be blocked easily. The appropriate transit analogy is to ticket vending machines, where 3-4 slowpokes can create long lines for everyone.

That’s why you have parallel berths. When you’re in the supermarket checkout with 5 lanes open, and one lane has a customer with a huge order, you go to another one, effectively skipping over that long delay. With a train, all passengers must be loaded before the train leaves, so all passengers must always wait the maximum duration.

Also, Alon, how can you claim that loading 1-4 passengers into a single vehicle on a level platform is slower than loading perhaps half a dozen or more people, all through a single narrow door, and up 2-3 steps? And we all know what effect the steps have on our “little old lady” or someone in a wheelchair, both of whom would walk/glide right onto a PRT vehicle with no steps to traverse.

Mike C: I think we have to clarify what a bus looks like nowadays. A bus has at least two double-wide doors on low floor level; an articulated bus has four double-wide doors on low floor level. A curb plus maybe kneeling technology will get you into the bus without steps.

By looking at the Heathrow vehicles, on the other hand, it is not possible to “just walk in … you have to bend and squeeze yourself into the seats, and if there are more than two people, it will get rather tight (particularly if there is more baggage than a little purse.

Of course, other applications may have different sized vehicles, where it is not such an issue.

Yes, some buses and LRT trains have level boarding. But this doesn’t come for free, as vehicles and stations with level boarding are more expensive than those without.

Again, my point is not that PRT is necessarily any more efficient at loading “little old ladies” than LRT or buses, only that it certainly is not LESS efficient, as Michael Setty implied in an earlier comment. Here is a YouTybe video of ATS founder Martin Lowson boarding an ULTra vehicle – it starts about 55 seconds into the clip. How can any argument be made that this PRT loading is less efficient than any bus or rail for anyone, including little old ladies and wheelchair-bound passengers?

PRT boards fewer people per vehicle. If there’s a line at a stop, it will take a lot longer to load everyone than it will to load one large train, because everyone after the first four has to wait while the pod leaves and wait for the next pod to arrive, etc.

It’s stupid to compare low-capacity vehicles to high-capacity vehicles; they serve different purposes. If you seriously want PRT to replace autos on roads, compare it with autos on roads.

New installations of bus/rail transit invariably have level boarding, as it makes complying with ADA much easier, and improves passenger experience in other ways. There is lots of existing rolling stock that requires climbing steps to board, but new deployments are mostly level-boarding.

Mike C: I’ll ask again — Can PRT handle the load of a single 10 or 20 story building of office workers? If 1,000 or 2,000 people need to get to the office between 8:45 and 9:00 am, can PRT handle that? If it can, how much station infrastructure does it need?

At any rate, that is a hell of a lot of pods. It can’t be cheap to buy, maintain, and store thousands of pods. Regardless of headways, it seems to me that the pure problem of dealing with one pod per person (or 1.2 people) would make the cost prohibitive during urban peak hour.

But of course, you have said that PRT is good for “moderate density” places, which I guess means low-slung parking-separated suburban office parks and single-family residential?

Also, Alon, how can you claim that loading 1-4 passengers into a single vehicle on a level platform is slower than loading perhaps half a dozen or more people, all through a single narrow door, and up 2-3 steps?

Reread the words “per passenger” in my comment.

Also, all modern LRT lines have level boarding; that’s already factored into the cost estimates, just as the LOLP is factored into capacity estimates.

So are you implying there is no middle ground between 20 story office buildings and suburban office parks?

Yes, 2000 people in 15 minutes would be a challenge for current generation PRT, as it would be for buses and many street level light rail systems which operate in the ~5000 pphpd range.

To answer your question, a one-second headway system (not here today, but likely will be in the next few years) can move >3000 vehicles per hour. If the PRT is laid out such that 2 bidirectional lines cross at or near the building, that’s 6000 veh/hr, 1500 every 15 minutes.

If the average round trip time is 10 minutes, that’s 6 trips every hour per PRT vehicle, so 6000 veh/hr throughput requires 1000 vehicles. At $50k per vehicle, that’s $50M.

Now much for light rail vehicles to support this? Let’s say 3-car trains running at grade, 5 minute frequency, 175pax/vehicle. That’s 3*12*175 = 6300. LRT trains will be required to travel the entire length of the line, and they also must stop at all stops, so assume round trip time of 20 minutes, so 4 trains are needed to service the rush. I believe modern LRT vehicles cost about $2-4M each, so 12 vehicles at $2-4M is $24-48M in vehicle costs for LRT to serve this demand.

So from a pure vehicle perspective, PRT might cost a little more, but it’s competitive. And every passenger gets a seat and a non-stop no-transfer trip.

Now, stations. 6000 veh/hr would certainly be a challenge, but not insurmountable. An 8-berth ULTra station with 20-seconds frequency per berth can move about 1440 veh/hr, so 4 would be needed. But recall, the LRT transit station is likely to be some distance outside of the building in question, perhaps 1/4 to 1/2 mile away, so those 4 PRT stations would need to be in about the same radius from the office building.

So could it be done? Yes. Should it be done TODAY? In my opinion, NO. Once again, there are plenty of cities where office buildings are 5 stories, not 20, and would require 1500-3000 passengers per hour, not 6000-8000. Many such cities are currently served almost exclusively by cars. PRT in such an application would provide an elegant transit alternative which will draw commuters out of their cars in significant numbers.

I feel like I’m repeating myself here, but it seems like people keep asking the same question in different ways, always implying that PRT must serve the highest density applications to be useful. Current generation PRT serves moderate density, small car-centric cities which are somewhere between a suburb and a big city in density. There are hundreds of such cities where PRT can be useful.

(The reason I answered the question on the 20-story office tower is to demonstrate that even in a moderately-high density environment, PRT COULD be useful down the road. Even if it’s not a good option today, it’s not as unrealistic as some people believe, and could become more viable as systems improve).

@Alon, I’ve answered it several different ways, but you still seem not to get it. Re-read what I wrote earlier and tell me: How and why would a LOL have a worse impact on PRT service and capacity than on buses or rail, when PRT vehicles are completely independent of one another?

Really, I don’t think you get what I’m saying. PRT loading is parallel and offline, bus/LRT loading is serial and inline, so in what circumstance would one slow passenger impact PRT more than buses and trains?

MIchael D #238. How would single occupant cars deal with the same case? About as good as the needed number of pods, but the station for the pods would only fill a fraction of the space needed for parking! Thereby freeing up additional leaseable space for the landlord.

If you build such a large commercial tower, it should be on a line-haul route for LRT or heavy rail. Most commercial zones have higher structures at the middle (accomodated by the line-haul) and gradual decrease in height/density as you go away which can be accomodated by the PRT as a local circulator; effective land use planning and PRT pricing can help encourage the desired result. As the local PRT circulators grow into each other, they can be interconnected.

Now turn Michael D’s question into a comparable 20 storey apartment: A typical modern condo tower in a CBD area might have 6 or 8 units units per floor. If you assume 2 people leave each unit during the peak hour, that is about 300 people which can be accomodated by perhaps 2 bays according to the numbers quoted above, and while their destinations would be reasonably well dispersed, it should probably be assumed that at least half (?) use the PRT to get to a line-haul station for access to regions unaccessible to the PRT network. Thus, every “satelite” PRT station will require extra bay(s) to be added to the tranfer station….design of these tranfer stations will be critical.

A similar case will occur if Heathrow’s system is extended from the parking lot to tie into the nearby hotels. Each hotel connected will require additional PRT bays to be provided at the terminal/HX/subway. At least in this case the travellers could be segregated to have some PRT bays designated for “hotels”, “parking”, etc.

Finally, I note that my assumptions above that many of the people want to go from a satellite to (the same) line-haul station would suggest that the ridesharing will be be higher than for a well-developed PRT network where no transfers are required.

How and why would a LOL have a worse impact on PRT service and capacity than on buses or rail?

Look, if the two explanations I’ve given don’t convince you, they don’t convince you. But I think the main issue isn’t even that. It’s that LRT capacity numbers are derived from real-world applications, which already factor in slack time to account for LOL and other delays, whereas PRT numbers do not.

OK, and I demonstrated how even a high LOLP (10%) would still result in no PRT guideway disruption at all and only 20% longer average per-berth cycle times in PRT stations, which can be resolved with ONE extra berth per station for the vast majority of stations. In many cases, the added berth would not even be needed, as the existing berths might already provide the excess capacity for the anticipated station demand.

And I suspect the real world LOLP during rush hour periods is MUCH less than 10%. Most people travelling at those times are commuters, not little old ladies, and I would guess that the percentage would be much closer to 1% than 10%. In fact, I think, contrary to what you say, that a very high percentage of very slow loading passengers would severely impact most existing transit systems, which are often not level boarding. If every station had a passenger which took 45 seconds to load during rush periods, thereby pushing all station dwells to 45 seconds, that would be noticeably disruptive on existing transit modes.

How often does it take 45 seconds for the train/bus to start during the rush period? At 10% LOLP, nearly every stop with more than 15 passengers would have one. The fact that it’s not currently a problem in existing modes is an indicator that even 10%/45 seconds are conservative (high) estimates, and even then the effect on PRT would be marginal.

PRT would handle such “human factors” fine.

But let’s consider another slow-loading scenario: wheelchair bound passengers. Most existing transit does not handle this well at all. Non-level boarding requires special elevated sections in stations. Many (most?) buses require lifts.

And, yes, modern designs are better, but upgrading existing systems would be expensive because every vehicle and every station would have to be changed. Not to mention, many underground rail systems don’t even have elevator access.

Even with the most modern rail vehicles and buses, the number of wheelchair-bound passengers which can be accommodated is generally limited – there’s no way every passenger on a bus/train can be wheelchair-bound, as with PRT.

Or, how about bicyclists? Many commuters who live far from the office like to take their bikes on transit. Existing transit systems either don’t allow bikes at all, or the bikes must be stored somewhere else in or on the vehicle. Even in this latter case, space is limited so that every passenger can’t take their bikes.

PRT accommodates all these situations, for all trips. So when your city hosts a Multiple Sclerosis convention and the wheelchair bound traffic suddenly spikes, PRT has it covered with little disruption. When there’s a bike race downtown and a large group of passengers suddenly need to board transit with their bikes, PRT has no problem.

Now, again, I’m not saying these scenarios can’t be dealt with in existing transit, only that Michael Setty’s assertion that PRT can’t handle them is wrong

Joe, the Heathrow system is fully constructed and is in testing. I believe the total overall delay has been less than 18 months, for a system unlike any other in the world.

They are proceeding cautiously. Sure, it would have been nice to see it open last year, but it’s more important to get it right. In fact, given the importance of this system for future development (the eyes of the world are on Heathrow right now, waiting for PRT to launch), I wouldn’t be surprised if there were more delays. The worst thing they could do is rush this to market.

As if that weren’t enough, a certain Professor Smeed at the University of London came up with the idea sixty years ago that expanding the road system to accommodate cars would be a bad idea, since it would merely lead in the long run to increased car use, and the expansion of car use would cancel out any relief to congestion that the new roads or new lanes were intended to provide. Governments in the UK ever since have been influenced by this idea, and have as a matter of policy strangulated the road system. Many towns in Britain have pedestrianized all or part of their central area, banishing the car outright, and London was one of the first cities in the world to introduce congestion charging.

This is such a load of crap I don’t even know where to begin. In the 1960s, after Smeed released his report concluding that expanding road capacity would not reduce congestion, Britain studied his report to death and did nothing.

You’re the one talking rubbish. The Smeed Report did not demand (or even explicitly recommend) road pricing. One thing Smeed, however, did recommend was refraining from building urban freeways, since doing so would, according to him, not result in traffic going faster (except temporarily). Here, the UK’s traffic planners did take Professor Smeed’s advice – not immediately, but soon afterwards – since not long after the report, the tendency to widen roads and build new roads in UK cities stopped almost completely. Other advice from Smeed, such as the introduction of speed limits, was also implemented.

As a result of Smeed’s advice, the UK has not seen the building of huge freeways such as cut through most large US cities. Quite to the contrary, there have been deliberate narrowings of roads, and the closing of many roads to cars. A recent example has been pedestrianization of two sides of Trafalgar Square. This is only a highly visible example of something that is repeated many times around London and other cities in the UK. In this, London’s transport planning shows the clear influence of Smeed’s ideas. This thinking in widespread in the UK. Apart from Birmingham in the 1960s, there are no cases of in Britain of substantial cities being significantly remodelled to make room for the car. Even Coventry, which was bombed out in WWII, so creating the necessity of massive postwar redevelopment of the centre, has, like many other UK cities, a substantially pedestrianized centre, and a ring-road system that is designed to keep cars away from that centre.

Most of your other stuff about the history and development of UK cities is factually wrong, also. I shall elaborate.

Most Britons do not live in rural areas, but most Britons do not live in dense cities, either (i.e. cities where it makes sense to spend $14-30 million/mile on fixed-guide transportation).

By North American standards, nearly all Britons live in dense cities (typically around 4-5,000 people per sq km, as opposed to about half that for large US cities, as this table illustrates: http://www.citymayors.com/statistics/largest-cities-density-125.html). It is interesting that you suggest that the cities most Britons live in are not dense enough to justify $14-30 million per mile on fixed-guide transportation. The UK government and local authorities obviously disagree, since they are very favourable to trains and trams generally, and the cost of implementing these projects is often higher than $14-30 million per mile. One project (the Jubilee line extension) cost £3.5 billion for 16 km – that’s US$566 million per mile.

The idea that they still live in medieval city boundaries is laughable. The medieval boundary of London is the City of London. The late 19th century boundary is most of Greater London, which itself is barely half the London metropolitan area.

Greater London is, almost by definition, the London metropolitan area. Greater London is surrounded by the Green Belt, which, as it’s name suggests, is not remotely metropolitan, so very little of metropolitan London extends beyond the Greater London boundaries. (Here’s a map, showing the developed areas and the official boundaries: http://en.wikipedia.org/wiki/File:Greater_london_outline_map_bw.png .) Beyond the Green Belt, we find the Home Counties, which includes towns that are considered part of the “Commuter Belt” (though they are not for the most part dormitory towns, but have their own commercial centres, often quite substantial – e.g., in Reading and Slough). This commuter belt is exceptionally well-served by trains. As I explained earlier, these towns grew up in the Victorian era, and are centred around Victorian train stations. These towns are much more car-friendly than London, but that’s not saying they’re on a par in that respect with LA. For example, they often have pedestrianized centres, and while North American cities such as LA typically have planning regulations such that businesses must ensure that they provide adequate parking for employees and customers, and property developers must ensure plenty of parking for residents, their British counterparts often have regulations with the opposite effect: they set highly restrictive maximum numbers of parking spaces that developers may provide.

Most of the London that Londoners live in today was built between about the mid-19th century and the 1930s. Building continued for a while after the war, with rebuilding of bombed-out areas, but has radically slowed down since the 1950s. Consequently, nearly everyone lives in a Victorian or Edwardian house, unless they live in a high-density council estate. The Victorian and Edwardian parts of London were not built with mass car ownership in mind. The streets in those areas are typically narrower than the streets in the Georgian (i.e., 18th to early 19th century) parts of London, such as the West End. There is no off-street parking for most houses, and there is not really any space on most residential streets, either — the streets are a good deal narrower than is typical in US residential areas. A high proportion are one-way, simply because there is no space for two moving lanes plus one or two parking lanes.

Most of the rest was built for cars: the 19th century cities in Northern England were depopulated after the war because of urban renewal schemes.

You’ve got that totally wrong. The Northern cities that boomed during the industrial revolution have lately suffered depopulation not because of urban renewal schemes, but because of deindustrialization. The industries on which they were built (from cotton weaving to car manufacturing) have moved elsewhere. The urban renewal schemes or not a causal factor in the depopulation – quite the opposite. Furthermore, the urban renewal schemes have not been, as you seem to be suggesting, anti-transit/pro-car. Again, the opposite is the case, and the building of mass transit (e.g., Manchester’s Metrolink) has played a big role in renewal schemes, as well as the building of high-density residential developments in or near city centres, in conformity with the ideas of “new urbanism”.

Where it wasn’t built for cars, cars don’t predominate: in Greater London, transit has a 52% mode share, private vehicles 37% (see table 1.8). And while the transit share has risen in response to congestion pricing, there was an equally large increase, driven mainly by a reduction in car traffic, in the years before 2003 (see table 1.6 in the above link).

Transit doesn’t have 52% mode share. You are either cherry picking furiously, or severely failing to understand the tables in that document. The tables you refer to are entitled “People entering central London during the morning peak” (table 1.6) and “Main mode of transport to work and mean time taken by Government Office Region and country of workplace”. In other words, both tables only look at trips to work. Trips that are not trips to work are much less likely to be conducted by mass transit. As the other tables clearly show, when you include all trips, the proportion involving cars rather than mass transit rises dramatically (http://www.dft.gov.uk/adobepdf/162469/221412/217792/4212241/transportstatisticgreatbrit.pdf). Furthermore, table 1.6 only refers to central London, and the statistic from table 1.8 is skewed by the large number of people who work in central London. Central London is notorious for having virtually no parking space at all for workers (and what little space exists costs in the region of £20 or more per day), so that public transport is the only realistic option for most. I once had to commute to central London. I took the train every day. The trains were always crowded, and I always had to stand for the whole one-hour trip. They were often delayed. Sometimes one had to let a train pass, because there was no room on board. It was hell, and it made me miserable. I hated every single day of it. I can assure you, very few people do that commute for fun.

If you want to continue evading the simple and obvious fact that cars are more more comfortable and nearly always more convenient than mass transit, fine, but in doing this you only betray your extreme bias. When you distort facts and cherry-pick data to the purpose of perpetuating that evasion, you merely discredit yourself.

But this whole thread discredits the opponents of PRT, since every argument they make has depended on faulty arithmetic or untrue “facts”. Your inaccurate portrait of the UK’s transport and planning history is just one inaccuracy of many. Shetty’s wild misinterpretation of the Lees-Miller paper and is one of the most egregious.

I’m glad you’re worried about misspelling people’s names when you conflate subway extensions with LRT, pretend most Britons live in central cities, and spread disinformation about mode share in London…

You have a cheek accusing me of spreading disinformation, when what I am doing is correcting your disinformation.

Most Britons live in towns and cities that are denser than US cities. The population is about 90% urbanized, and the average density of urban areas is considerably higher than that in the US. Street layouts date back mainly to the era before mass car ownership. All this is quite contrary to the impression that you tried to convey. Urban renewal in the North did not cause depopulation as you suggested, nor was it car oriented, but in fact often involved pedestrianization and/or upgrading of public transport.

You tried to give the impression that the car is favoured by government policy and expenditure, etc., in Britain, relative to public transport, and that most urban areas in the UK are designed around the car. Practically everything you said about driving, roads and urban planning in the UK is the directly contradicted by the facts. Simply, you were spreading disinformation, and I corrected you.

We’re talking about the country that has the least motorway per capita among the EU15 (less than half as much as most other countries in that group), the country that for several years imposed an nationwide moratorium on road-building, the country that has the highest fuel duties in the whole EU, the country all of whose largest cities acquired most of their present size before the majority of people owned cars, and thus whose street-plans are not designed around the car, the country where freeways are conspicuous by their absence.

It is simply crazy to suggest that the above-described country is a country where people drive because driving is subsidized and/or encouraged by the state. You engage in blatant cherry-picking of data when you take a country where nearly 90% of km traveled are by car, as opposed to around 6% by train, and try to convey the impression that the train is more popular than the car by selecting an outlying single datum that would seem (misleadingly) to support that, namely, trips to work in London. Right next to table 1.6 in the document you cited is table 1.5, which shows that, while public transport’s share of commuter traffic in the UK is 22%, its share of non-commuter traffic is a third less, at just 14% (and even this figure is biased in favour of public transport, because of how it represents mixed-mode trips). So trips to work do not tell the whole picture.

All your disinformation is aimed at supporting the false notion that mass transit is the ideal form of ground passenger transport, and people have no rational grounds for preferring other modes. The truth, which you persistently evade, is that, whatever the downsides of the car regarding, e.g., pollution and land-use issues, travel by car is usually faster, more convenient, more flexible and more comfortable than travel by mass transit, and these quite rational considerations, rather than any conspiracy by governments or corporations to favour the car, explain the car’s persistent popularity. It is not feasible to upgrade mass transit the the point where it is as attractive as the car, therefore, without authoritarian measures or some kind of spectacular economic collapse or extreme fuel shortage, mass transit will never dominate ground passenger transport. If you want to support a public transport system that does have the possibility of attracting a high proportion of ridership away from cars, then PRT is far more promising than trains and buses, whose relative unattractiveness to riders is proven.

On the ULTRA website, it is written that the protection sytem is based on a fixed block system inside the guideway. Does anyone has information on that ? I can’t understand that finally they don’t use use only the distance to the leader inside the pod to provide safety. This is totally in contradiction with the PRT goals … and it totally mimick the railway system. The only thing that remains is thus the on demand. I suppose taht they were unable too proce the safety of the pod independantly thus they had to rely on another system.

They don’t even use moving blocks thus the pod speed won’t be taken into account in pod distance. Maybe this is the reason for the delay because the safety was not considered sufficient ? If the headway is increased too much, the detection system inside the pod has not enough range to detect the leader pod or is unable to see through the curve and grade. Thus you must have an alternate system to see further and keep a sufficient distance ahead.